turkey earthquake 2011 case study

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Van earthquake of 2011

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• National Earthquake Hazards Reduction Program - Collaborating and Assisting in Turkey
• Disaster and Emergency Management Authority - About Van Earthquake
• The Economist - Death in the Afternoon
• Mukogawa Women's University - The 2011 Van Earthquakes Ocurred in Turkey
• Earthquake Engineering Research Institute - The M.w 7.1 Erciş-Van, Turkey Earthquake of October 23, 2011
• International Federation of Red Cross and Red Crescent Societies - Emergency Appeal Operation Update Turkey: Van Earthquake
• National Center for Biotechnology Information - PubMed Central - The October 23, 2011, Van (Turkey) earthquake and its relationship with neighbouring structures

Van earthquake of 2011 , severe earthquake that struck near the cities of Erciş and Van in eastern Turkey on October 23, 2011. More than 570 people were killed, and thousands of structures in Erciş, Van , and other nearby towns were destroyed. The earthquake was felt as far away as Jordan and southern Russia .

The initial shock, which registered a moment magnitude of 7.2, struck at 1:41 pm local time. Its epicentre was about 10 miles (16 km) northeast of Van, and its focus was 12.4 miles (about 20 km) underground. A magnitude-6.0 aftershock , one of more than 200 such events that were recorded in eastern Turkey within the first 24 hours after the earthquake, struck at 11:45 pm the same day some 15.5 miles (25 km) from the epicentre of the initial earthquake.

The earthquake and its aftershocks were the result of rock fracturing that relieved compressional pressure between the Eurasian Plate and the Arabian Plate, which subducts (underthrusts) under the Eurasian Plate at an average rate of 0.94 inch (24 mm) per year. The earthquake’s epicentre occurred about 50 miles (about 80 km) north of the Bitlis Suture Zone, a complex geologic region characterized by rock folding and a series of three large northward-dipping thrust faults (a fault type in which older rocks are forced up and over younger ones). In a manner consistent with other earthquakes in this region, the intense compressional forces occurring between the plates resulted in oblique thrust faulting (faulting characterized by horizontal as well as vertical movement) when the rocks at the epicentre gave way.

Turkey’s Ministry of Health and the Turkish Red Crescent directed the rescue and relief effort. Those two organizations collaborated with a number of other national and international aid agencies to assemble and deliver field kitchens as well as thousands of tents , blankets, and portable heaters to the region. Almost immediately after the quake, several thousand aid workers, including a large number from dozens of nearby settlements, descended on the earthquake zone, while the Turkish army searched adjacent mountainous areas for survivors and additional casualties.

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• Published: 12 March 2014

The October 23, 2011, Van (Turkey) earthquake and its relationship with neighbouring structures

• Moro M. 1 ,
• Cannelli V. 1 ,
• Chini M. 2 ,
• Bignami C. 1 ,
• Melini D. 1 ,
• Stramondo S. 1 ,
• Saroli M. 1 , 3 ,
• Picchiani M. 1 ,
• Kyriakopoulos C. 4 &
• Brunori C. A. 1  

Scientific Reports volume  4 , Article number:  3959 ( 2014 ) Cite this article

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The present work reports the analysis of a possible relationship due to stress transfer between the two earthquakes that hit the province of Van, Eastern Turkey, on October 23, 2011 (Mw = 7.2) and on November 9, 2011 (Mw = 5.6). The surface displacement field of the mainshock has been obtained through a combined data set made up of differential interferograms from COSMO-SkyMed and ENVISAT satellites, integrated with continuous GPS recordings from the Turkish TUSAGA-AKTIF network. This allowed us to retrieve the geometry and the slip distribution of the seismic source and to compute the Coulomb Failure Function (CFF) variation on the aftershock plane, in order to assess a possible causal relationship between the two events. Our results show that the November 9 earthquake could have been triggered by the October 23 shock, with transferred stress values largely exceeding 1 bar.

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Introduction.

The occurrence of a seismic event perturbs the stress field within the Earth crust, altering the probability of occurrence of a second strong event along nearby faults. This phenomenon is known as fault interaction and the physical mechanism at its basis is known as the Coulomb Stress Triggering 1 . In literature it has been shown that even weak increments of stress can trigger large seismic events 2 , if the relative seismogenic structures are close to the end of their seismic cycle; furthermore, the interaction between two seismic events may occur both within long interseismic periods 3 and smaller time intervals 4 , 5 , 6 . Stress field perturbations cannot be instrumentally detected, but can be numerically simulated by means of mathematical models 2 , 7 , 8 , 9 . Several studies demonstrate that the distribution of aftershocks and the variations of the seismicity rates are generally explained in terms of the Coulomb failure criterion 1 , 2 , 10 , 11 , 12 , which allows to interpret a shear stress exceeding a certain fraction of the normal stress as an increased probability of failure 10 . Several physical-static prediction models based on the Coulomb criterion have been proposed 13 , 14 ; these models have been widely applied for the redefinition of the regional seismic hazard following earthquakes 12 , 15 , 16 , 17 , 18 .

The province of Van (Eastern Turkey) has been struck by two strong earthquakes in a few days. The first earthquake occurred on October 23, 2011 (Mw = 7.2), 30 km N of Van city, while the second took place on November 9, 2011 (Mw = 5.6) few kilometers to the South 19 ( Fig. 1a ), in the Edremit subprovince. A significant aftershock activity was recorded after the first shock over the Van region ( Fig. 1a ). The Mw 7.2 Van earthquake occurred along a ENE-WSW fault, previously recognized by Kein 20 , who attributes to it a main right lateral strike slip mechanism. However the CMT (Centroid Moment Tensor) solution from USGS and GFZ indicates a pure reverse fault mechanism ( Fig. 1a ) 21 , 22 , while the Harvard CMT solution is a mixed reverse-right lateral mechanism. Concerning the November 9 (hereafter Edremit-Van) earthquake, the Kandilli Observatory and Earthquake Research Institute (KOERI) CMT solution indicates a dominant strike slip mechanism 23 .

(A) Aftershocks distribution following the October 23, 2011, mainshock: in blue up to November 9, 2011, earthquake; in yellow since November 9 and till November 30, 2011. Red lines represents the main active faults in the area, modified from SHARE “Seismic Hazard Harmonization in Europe” ( www.share-eu.org ). Figure 1A is not released under a Creative Commons Attribution-NonCommercial-ShareALike 3.0 Unported License. This image is licensed under a separate, Creative Commons Attribution-ShareAlike 3.0 Unported License. To view a copy of this licence visit http://creativecommons.org/licenses/by-sa/3.0/ . (B) Tectonic setting of the Eastern Mediterranean region. White and black arrows indicate the plate motion versus. Maps created with ARCGIS 10 software.

Turkey is surrounded by three main plates, the African, Eurasian and Arabian ones, characterized by relevant tectonic activity. Other two minor plates are also present in this region, the Aegean and the Anatolian ones. The relative motion amongst the above mentioned plates has generated some of the major tectonic features of Turkey: the Aegean Arc, the West Anatolian Graben Complexes, the North Anatolian Fault Zone, the East Anatolian Fault Zone, the North East Anatolian Fault Zone, the Bitlis Thrust Zone and the Caucasus ( Fig. 1b ) 24 . The study area is located where the Arabian Plate, that moves towards north-northeast, collides with the Eurasia along the Bitlis Thrust Zone, a complex collisional boundary located north of the fold-and-thrust belt of the Arabian platform. This suture zone corresponds with the Van Lake region from which the other smaller plates move symmetrically away, forced by the Arabian plate movement (see Fig. 1b ) 25 . In this sector the GPS velocities indicate a NW-oriented motion of 18 ± 2 mm/yr relative to the Eurasia 26 , causing an intense seismic activity. This latter is associated with ENE-WSW and NW-SE conjugate strike-slip faults, of dextral and sinistral character, parallel to the North and the East Anatolian fault zones. Among the major structures in the area the Çaldıran Fault, Erciş Fault, Iğdır Fault, Malazgirt Fault, Süphan Fault, Kağızman Fault Zone, Tutak Fault Zone and Northeast Anatolian Fault Zone can also be mentioned. These structures are compatible with NNE-SSW compression and WNW-ESE extension in the region that well-matched the reverse mechanism related to the Van earthquake.

Several large earthquakes have struck this region both in historical and instrumental ages. The most relevant known that damaged the city of Van was the 1648 event (March 31, Mw ≈ 6.6), which has been associated with the E-W trending Gurpinar thrust, located south of Van 27 . The 1715 event (March 8, Mw ≈ 6.6) was located between the eastern termination of Derik fault and Van 28 , whilst the 1903 (April 28, Mw ≈ 7) Malazgirt earthquake occurred on a NNE-SSW trending structure 29 . One of the most recent and destructive event was the November 24, 1976 (Ms = 7.3), Caldiran earthquake, causing more than 4,000 casualties and intense damaging in a 2,000 km 2 area 30 . The responsible fault was a N 110°–135°, 50 km long, right lateral strike-slip mechanism, with observed horizontal displacements varying between 2.5 and 3.5 m and a vertical displacement of about 50 cm.

We have applied Differential Interferometric SAR (DInSAR) technique to investigate the surface displacement due to the 2011 Mw 7.2 and Mw 5.6 shocks. Different datasets have been used. In order to study the mainshock, a pair of COSMO-SkyMed Stripmap data has been processed, together with two ENVISAT SAR images. An additional dataset composed of two TerraSAR-X pairs was available to measure the surface effects induced by the second event and to infer its fault geometry. Finally, in order to remove the topographic phase contribution, we used the Shuttle Radar Topographic Mission (SRTM) digital elevation model. To better constrain the deformation field, we integrated in our analysis the DInSAR dataset with coseismic displacement field from 20 GPS stations belonging to the Turkish CGPS network, whose static offsets was assembled by Dr. Rahsan Cakmak (TUBITAK MRC EMSI) and are available at http://supersites.earthobservations.org/van.php .

DinSAR processing has been applied to a SAR dataset composed of three pairs of Very High Resolution (VHR) X-band images (in stripmap mode 31 , 32 ), one acquired from COSMO-SkyMed (10/10/2011–23/10/2011), i.e. related to the main event and the other two from TerraSAR-X (9/11/2011–20/11/2011 and 31/10/2011–11/11/2011) satellites. The frame available from COSMO-SkyMed partially covers the epicentral region, with the epicenter of October 23 mainshock located few km out of the area of measurement ( Fig. 2 ). The measured surface movements have a maximum deformation along the LOS (Line Of Sight) of about 1.0 m in the uplifting sector, while in the southern portion of the interferogram a subsidence up to 0.02 m has been detected. As the COSMO-SkyMed images did not cover the northern section of the deformed area, a pair of SAR images acquired by ENVISAT platform (22/07/2011–19/11/2011) has been used in order to better assess the induced surface displacement in the upper region of the displacement field, ( Fig. 2 ). Despite the ENVISAT data pair covers a time interval including the November 9 event, the northern portion of the displacement field can be considered free of the effects of the second earthquake because of to the large epicentral distance. Two TerraSAR-X interferograms, along descending and ascending orbits ( Supplementary material Fig. S1 ), have been used to investigate the effects of the November 9 earthquake. These interferograms clearly highlighted that the November 9 event did not contribute to the deformation induced by the main shock on October 23.

Mosaic of unwrapped differential interferograms relative to the October 23, 2011 earthquake, from COSMO-SkyMed and ENVISAT coseismic pairs (south and north of the dashed line respectively).

The ENVISAT dataset has been scaled to compensate the small discontinuity with respect to COSMO-SkyMed data mainly due to a different reference point selected for the unwrapping procedure and the different LOS of the two satellites. The displacement is in LOS geometry. Maps created with ARCGIS 10 software.

TerraSAR-X interferograms show different fringe patterns, probably due to the strike slip mechanism, that implies most of the movement along an horizontal axis. Unfortunately TerraSAR-X data do not allow to solve the ambiguity of the E-W and N-S conjugate planes, either because the coseismic displacement field is partially detected, or due to the moderate magnitude of the buried fault. Nevertheless, the E-W plane solution can be considered the most probable as suggested by Akinci et al. 33 and supported by field evidence 34 .

We retrieved the source model for the Van earthquake from a two-step joint inversion of DInSAR and GPS data. In a first step, the geometry and extension of the source have been determined assuming uniform slip on the fault plane. The probability distributions of the fault plane parameters ( Fig. S2 ) have been obtained by evaluating the Bayesian integrals with a numerical Markov-Chain Monte Carlo integration scheme 35 . The most probable model ( Table 1 ) has a strike of 252 degrees and dips NNW at 50 degrees. The strike value is consistent with the orientation of the CMT focal plane and with geodetic models 36 , 37 . The modeled dip angle is slightly larger than the value from Harvard CMT, but is consistent with geodetic indications of a steeply dipping fault in the range 40–55 degrees 37 . The geodetic magnitude for the uniform-slip model is M = 7.08 if a shear crustal modulus of 30 GPa is assumed.

After the definition of the fault geometry, a linear inversion has been performed in order to estimate the slip distribution on the rupture plane. In this step, the size of the fault plane has been extended in order to better account for slip heterogeneities. The resulting slip distribution is shown in Figure 3 and has a cumulative geodetic magnitude of M = 7.12, in good agreement with the seismological estimates. The resulting pattern shows a deep high-slip patch, with peak slip (3.8 m) located at 15 km depth, with the epicentral location (provided by KOERI) located at its lower boundary; the location and extents of the bulk slip area is consistent with results by Fielding et al. 36 . This geometry suggests that the rupture nucleated in the deep central portion of the fault and migrated towards the surface. The direction of slip vectors show dominant reverse-left mechanism; a patch with moderate reverse-right slip values at the southeastern tip of the modeled fault is probably an artifact, because this edge of the fault is beneath water and therefore is not constrained by SAR data. The modeled deformation field ( Figures 4a and 4b ) reproduces correctly the observed displacement; residuals of a few centimeters found on the eastern portion of the fault plane surface trace may be ascribed to a change in the strike direction 37 , and/or to the activation of secondary shallow ruptures 38 .

Slip distribution model for the October 23, 2011 event A yellow star mark the epicentral location provided by KOERI.

A red box mark the position and extents of the fault plane obtained in the nonlinear inversion step. Maps created with GMT software.

(A) Observed (left) and modeled (center) DInSAR deformation fields.

Residuals (right) are defined as the difference between observed and modeled displacements. The surface projection of the source model is also shown as a dashed box. The vertical shift between the COSMO-SkyMed and ENVISAT displacement is due to the different absolute references for the two datasets. (B) Observed and modeled horizontal (left panel) and vertical (right panel) GPS deformation fields. Error ellipses in the left panel and vertical bars in the right panel correspond to 68% confidence levels. The GPS offsets show a compressional deformation regime, consistently with the expected thrust mechanism; the largest offset of about 6 cm is found at the near-field site MURA. Maps created with the GMT software.

Once defined the source model for the Van earthquake, the role of this event in promoting the rupture of the Van-Edremit earthquake through a Coulomb Failure Function (CFF) analysis can assessed. The CFF is evaluated by computing the incremental stress tensor produced by the elastic dislocation of the Van earthquake, projecting it on the rupture plane of the Van-Edremit earthquake and evaluating the relative contributions of the normal and shear stresses. Positive or negative variations of the CFF indicate that the perturbation to stress field is acting to promote or oppose the rupture, respectively. Since there is no information available to reliably identify the rupture geometry of the Edremit-Van event between the two Harvard CMT conjugate planes, we computed the CFF variation on both planes. The two planes are centered on the hypocentral location given by KOERI (43.234N, 38.430E), with dimensions 15 × 10 km 2 , covering a depth range of about 0–10 km. In Fig. 5 we show the variation of CFF resulting on the two CMT planes. Both planes are loaded with positive CFF variations, with average values of 1.3 bar and 1.1 bar for the E-W and N-S planes, respectively. Peak CFF values (2.6 bar for the E-W plane and 3.0 bar for the N-S plane) are found on the deep portion for both planes.

CFF variations induced by the October 23, 2011 event on the November 9, 2011 rupture plane for both Harvard CMT solutions.

In the left panel, a red box marks the position of the modeled fault plane for the mainshock, while black boxes mark the positions of both CMT nodal planes. Maps created with the GMT software.

We have investigated the Van earthquake (October 23, 2011) by applying DInSAR technique and exploiting the capabilities of the VHR SAR data acquired by COSMO-SkyMed and the C-band ENVISAT images. The COSMO-SkyMed differential interferogram has allowed to retrieve the surface displacement field. Since the DInSAR data does not cover the region located to the north of the event, we integrated SAR measurements with coseismic GPS offsets from the Turkish geodetic network.

The inference of the October 23 seismic source on the basis of geodetic data has been the subject of a set of studies 36 , 37 . Fielding et al. 37 modeled the rupture as a single fault plane using SAR, GPS and seismic waveform data. On the other hand, Elliott et al. 36 modeled surface displacements from COSMO-SkyMed and ENVISAT with a pair en-echelon fault planes. Both studies indicate a deep rupture, with significant slip at 8 km depth, a dip range between 40 and 54 degrees. In our analysis, we modeled the fault with a single plane. Our most probable solution has a mixed thrust-left slip on a plane dipping NNW at about 50 degrees, consistently with the cited results even if slightly larger than the dip from Harvard CMT. Moreover the strike is consistent with seismological and geodetic estimate. Most of the slip occurs on a patch of about 15 × 10 km 2 , approximately located at depths between 10 and 18 km. The location and extents of the high slip patch is consistent with the peak slip area obtained by Fielding et al. 37 . Probability density functions for model parameters ( Fig. S2 ) shows that the position, geometry and along-strike extents of the fault plane are well resolved, while trade-offs exist among depth, slip and along-dip extents, which is a well-known limitation of geodetic source inversions 39 . The highest residuals ( Fig. 4a ) are in the central part of the northern edge of the COSMO-SkyMed frame, where boundary effects maybe present and along the eastern portion of the fault surface trace, supporting the hypothesis of a discontinuity in the strike direction as suggested by Elliot et al. 36 . GPS horizontal offsets ( Fig. 4b ) are well recovered by the model, while the largest offsets (at sites MURA and OZAL) in the vertical component are overestimated, even though residuals are well within a standard deviation.

Finally, we investigated the effect of the perturbation to regional stress field induced by the mainshock on the November 9 earthquake through the evaluation of the CFF variation. For the Edremit-Van earthquake, Harvard CMT solution provides a N-S and an E-W conjugate planes, both with strike-slip geometries.The E-W plane is the most convincing; this conclusion is supported by field evidences found by Selcuk et al. 34 . However, since it is not possible at present to reliably solve the ambiguity between the two geometries, the CFF variation has been computed on the two conjugate planes ( Fig. 5 ). We found that both are loaded with stress levels up to 2.5–3.0 bar, largely exceeding the threshold value of 0.1 bar that is widely used to assess effective triggering of seismic events 3 , 10 . These findings, in agreement with previous results by Akinci & Antonioli 33 , support the hypothesis that the Edremit-Van earthquake has been actively promoted by the October 23 Van event.

In order to study the surface effect of the two main events, we have applied DInSAR method to a dataset composed of four pairs of images. The first, one was acquired by the Italian COSMO-SkyMed satellite, the second one by the European ENVISAT platform and the two other pairs by the German TerraSAR-X. COSMO-SkyMed and TerraSAR-X satellites are equipped with an active X-band microwave sensor, while ENVISAT SAR is a C-band system, all capable to achieve cloud-free and day-and-night land observations. The X-band images are acquired in Stripmap mode at 3 m spatial resolution and the ENVISAT data are in IS6 mode ( https://earth.esa.int/handbooks/asar/ ), at about 20 m spatial resolution. The COSMO-SkyMed and ENVISAT data, both along ascending orbit, have been used to investigate the October 23 mainshock. In particular, the post-event image of COSMO-SkyMed is dated October 23, only few hours after the seismic event, while pre-seismic one was acquired on October 10, 2011. The ENVISAT scenes were taken on July 22, 2011 and November 19, 2011. It is worth to note that the time interval between these two images includes also the strong aftershock occurred on November 9. We selected from ENVISAT interferogram the portion that complete to the north the surface displacement measured from COSMO-SkyMed dataset (see Fig. 2 ) and which was not affected by the November aftershock, as confirmed by TerraSAR-X interferograms.

TerraSAR-X images have been used to measure the deformation caused by the November 9, 2011, earthquake. In this case for the descending pair, the pre-seismic image is acquired few hours before the earthquake, while the post-seismic one is dated November 20, 2011. Concerning the ascending pair, the pre-seismic image is ten days before the earthquake (31/10/2011), the post-seismic image two days after (11/11/2011).

In order to improve the signal-to-noise ratio, a 2 by 2 multi-look factor in slant-range and azimuth has been applied to the COSMO-SkyMed and TerraSAR-X interferograms, with a square pixel of about 6 m. The 90 m Shuttle Radar Topography Mission (SRTM) digital elevation model has been used to remove the topographic contribution of the interferometric phase. Since the temporal baseline is sufficiently short, both interferograms maintain a good coherence, allowing capturing most of the coseismic deformation. Before the retrieval of the Line Of Sight (LOS) displacements using a minimum cost flow phase unwrapping algorithm, the phase noise has been reduced applying an adaptive filter 40 .

Concerning the lower resolution data coming from ENVISAT, we computed the interferogram by using a multi-look factor equal to 1 × 5, in range and azimuth respectively and by applying the same phase noise reduction and unwrapping methods of X-band data. DORIS precise orbital data have been used to correct possible orbital fringes. Despite the low interferometric coherence of ENVISAT interferogram, caused by the long time interval (temporal baseline), the unwrapped data have contributed to improve the spatial coverage and to better constrain the model retrieval.

We jointly inverted DInSAR (COSMO-SkyMed and ENVISAT) and GPS data using a two-step method: we first inferred the geometric features of the Van earthquake source with a non-linear inversion assuming a uniform slip, then we retrieved the slip distribution on the fault plane with a linear inversion. For the inversion procedure, a combined DInSAR deformation field has been obtained by selecting the ENVISAT field laying in the region not covered by COSMO-SkyMed data and merging this subfield with the full COSMO-SkyMed field. In regions where both datasets are available, we used only the COSMO-SkyMed dataset that, because of its shorter temporal baseline, it is less affected by post-seismic effects. The resulting combined dataset has been downsampled by a factor of 0.5 for computational reasons.

For the nonlinear inversion procedure we modeled the deformation field for a given fault plane using the analytical expressions from Okada 41 , assuming an homogeneous Poisson half-space. To take into account the different characteristics of DInSAR and GPS datasets, we applied different weights to each in order to obtain similar contributions to the total misfit for models that give an equivalent fit to the data. We used a Bayesian inference scheme to estimate the probabilty distribution functions (PDF) of fault parameters through a Markov-chain Monte Carlo integration 35 . Since the COSMO-SkyMed and ENVISAT datasets have different absolute references, we included in the model parameters a “bias” value between the two datasets.

Once the geometry is fixed, we estimated the slip distribution on the fault plane with a linear inversion. We extended the fault plane resulting from the uniform inversion up to 40 × 30 km 2 in order to better account for (eventual) slip heterogeneities and subdivided it into patches of size of about 1.5 × 1.5 km 2 We composed a Green Function matrix by imposing a unitary slip on each patch and computing the corresponding deformation fields for DInSAR and GPS data, according to the Okada analytical expressions 41 . The slip distribution is then recovered by simultaneously minimizing (in the least-squares sense) the total chi-squared and a discrete approximation of the Laplacian to avoid large, unphysical oscillations in slip values. The solution is computed assuming a positivity constraint on the model, with an optimized version of the Lawson-Hanson method 42 , 43 . The inclusion of a smoothing term to damp unphysical model oscillations introduces a tradeoff between data fit and solution roughness. We determined the weight of the smoothing constraint by evaluating a misfit-roughness tradeoff curve ( figure S3 ).

We estimated the spatial resolution for the slip distribution on fault plane by defining a checkerboard synthetic slip model. The resulting slip distributions have been computed with the coverage of SAR and GPS data and inverted with the same procedure used for the real datasets. Results ( Figure S4 ) show that a resolution of about 5 km can be expected up to ~5 km depth, while at greater depths model resolution decreases to over 10 km.

We then investigated the role of the Van earthquake in promoting the rupture of the Van-Edremit earthquake by evaluating the Coulomb Failure Function (CFF). Using the source model obtained for the Van earthquake, the elastic strain tensor corresponding to the seismic dislocation is computed with the analytical solutions provided by Okada 41 . Using standard relations from elasticity theory, the strain field is converted into an incremental stress tensor that acts as a perturbation of the pre-existing (unknown) regional stress field. The effect of the perturbation to the stress field on a given fault mechanism is then assessed by computing the CFF variation, defined as ΔCFF = Δτ + μ(Δσ n + Δp), where Δτ and Δσ n are respectively the shear and normal incremental stresses, μ is the friction coefficient and Δp is the pore pressure change 44 . It is convenient to rewrite this relation as ΔCFF = Δτ + μ e Δσ n , where μ e is an effective friction coefficient taking into account static friction, hydrostatic pressure and pore fluid pressure 3 , 7 . We assumed μ e = 0.4, a value consistent with laboratory evidences on friction and moderate pore pressure in conditions where fluids are not fully expelled 45 . Knowing the values of ΔCFF on a given fault mechanism allows to establish whether the stress field is acting to promote (ΔCFF > 0) or oppose (ΔCFF < 0) the rupture. As a general rule, a CFF increase of 0.1 bar (corresponding to tidal load) is considered in literature as effective for earthquake triggering 3 , 10 .

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Acknowledgements

We would thank Dr. Can Zulfikar from KOERI (Istanbul) for his contribution to find scientific documents and reports concerning the Van earthquake. We also thank Dr. Semih Ergintav for providing GPS data. Marco Chini's contribution was supported by the National Research Fund of Luxembourg through the PAPARAZZI project (CORE C11/SR/1277979).

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M.M. contributed to the analysis of seismotectonic regime of the region and the analysis of the results. M.C. and C.B. contributed to the DInSAR processing. V.C. and D.M. have provided the cff and source models. S.S. contributed to the analysis of the results and the discussion. M.S., M.P., C.K. and C.A.B. contributed to the discussion of the results. All authors contributed to write the manuscript.

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Moro M., Cannelli V., Chini M. et al. The October 23, 2011, Van (Turkey) earthquake and its relationship with neighbouring structures. Sci Rep 4 , 3959 (2014). https://doi.org/10.1038/srep03959

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The 2011 Mw 7.1 Van (Eastern Turkey) earthquake

We use interferometric synthetic aperture radar (InSAR), body wave seismology, satellite imagery, and field observations to constrain the fault parameters of the M w  7.1 2011 Van (Eastern Turkey) reverse-slip earthquake, in the Turkish-Iranian plateau. Distributed slip models from elastic dislocation modeling of the InSAR surface displacements from ENVISAT and COSMO-SkyMed interferograms indicate up to 9 m of reverse and oblique slip on a pair of en echelon NW 40 °–54 ° dipping fault planes which have surface extensions projecting to just 10 km north of the city of Van. The slip remained buried and is relatively deep, with a centroid depth of 14 km, and the rupture reaching only within 8–9 km of the surface, consistent with the lack of significant ground rupture. The up-dip extension of this modeled WSW striking fault plane coincides with field observations of weak ground deformation seen on the western of the two fault segments and has a dip consistent with that seen at the surface in fault gouge exposed in Quaternary sediments. No significant coseismic slip is found in the upper 8 km of the crust above the main slip patches, except for a small region on the eastern segment potentially resulting from the M w  5.9 aftershock on the same day. We perform extensive resolution tests on the data to confirm the robustness of the observed slip deficit in the shallow crust. We resolve a steep gradient in displacement at the point where the planes of the two fault segments ends are inferred to abut at depth, possibly exerting some structural control on rupture extent.

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Simple Models of Complex Slip Distribution? A Case Study of the 2011  M w 7.1 Van (Eastern Turkey) Earthquake

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We evaluate the presently proposed simple models for slip distribution, including the homogeneous slip model, the triangular slip model, the k -square model, the slip tip taper model, and the restricted stochastic source model, to investigate which is most consistent with ‘real-world’ slip distribution inverted. We take the 2011 Van (Eastern Turkey) M w 7.1 earthquake as an example, considering six inversion results of slip distribution. The Akaike information criterion (AIC) is used to evaluate the models. The evaluation shows that for six inversion results, qualitatively, the k -square model, with three degrees of freedom, seems most consistent with the real-world slip distribution overall.

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Acknowledgements

We thank Prof. Max Wyss for helpful remarks on the text. We thank Prof. Lisheng Xu, Prof. Yong Zhang and Dr. Xu Zhang for discussions about the finite-fault seismic source inversion.

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Li, J., Wu, Z., Jiang, C. et al. Simple Models of Complex Slip Distribution? A Case Study of the 2011  M w 7.1 Van (Eastern Turkey) Earthquake. Pure Appl. Geophys. 177 , 387–395 (2020). https://doi.org/10.1007/s00024-019-02167-7

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Van, Turkey Earthquake of 23 October 2011, Mw 7.2; An Overview on Disaster Management

Mehdi zarÉ.

1 International Institute of Earthquake Engineering and Seismology, Tehran, Iran

Behnaz NAZMAZAR

2 Northern Tehran Branch, Islamic Azad University, Tehran, Iran

An earthquake was happened on 23 October 2011 in Van, Turkey (Mw7.2) at the eastern most area of Anatolian plateau and in the neighborhood of Iranian border (West Azerbaijan Province). The study was performed based on field and office observations and has been focused on the process of disaster management in Turkey after the 23 October 2011 earthquake. We surveyed the quake from the view point of disaster management, and study the relief process during and after the catastrophe. The day-to-day disaster management procedure in seventeen days after the event has been scrutinized as well. The number of victims and extent of damage in Van earthquake was relatively limited according to the national experiences and recent modernization of infrastructures in Turkey. The Van earthquake caused 644 deaths and demolishing of several buildings in the cities of Van and Erciş in Van Province. The performance of the government organizations is however criticized based on their response to the event.

Introduction

In 23 October 2011, at 13:41, local time, an earthquake jolted eastern Turkey (Van Province) for about 25 seconds. In its first assessment, Kandilli Observatory and Earthquake Research Institute (KOERI, Bogaziçi University) announced the quake magnitude to be ML6.6 and its epicenter in Tabanli village, north of the city of Van. Disaster and Emergency Management Presidency of Turkey (in Turkish; Afet ve Acil Durum Yönetimi Başkanlığı, AFAD) announced dispatching of more than 1275 savior and nurse from 45 provinces and 37 different institutes to Van, immediately after the event. AFAD 20 person committee reached to region immediately and 200 technicians from different provinces devoted to help the hurt people. Moreover, AFAD designated a coordinator and an envoy three major airports of Ankara Esenboða, Istanbul Ataturk and Izmir Adnan Mendres, in order to organize the save and rescue (SAR) groups and the first aids, medical and service persons. Turkish Red Crescent (Türk Kızılayı) as a contribution to public service intervening in disasters coordinating with units as AFAD, fire stations and therapeutic centers. All of the follow up search and rescue actions being coordinated at the center of AFAD, and Turkish Red Crescent was a part of the incident national response structure and in the circle of command centers affairs.

The method we applied was disaster relief provided to the disaster-affected population of Van and Ercis after the 23 October 2011 earthquake in Turkey. The intention of performing this study was to evaluate the actions and to review the process of the management after the Van earthquake of 23 October 2011. Therefore it is not only an executive report, but is a fresh eye witness to what had done in view point of disaster management after the Van earthquake. Our team attended in the earthquake prone area therefore this article summarizes our study based on a day by day focusing on what happened after the Van earthquake and finally a conclusion is provided on these observations. This way of disaster management surveying is provided as well in many other studies (i.e. ( 1 , 2 ) on the integrated approach to natural disaster management and as a case study on the January 2001 Earthquake in Gujarat, India (prehospital and disaster medicine).

Rescuing operations

Turkish Red Crescent Society, immediately after informing about the quake, held its disaster management meeting at Disaster Management Center (HQ) and alarmed the other centers in North Anatolia (Erzurum), North East Anatolia (Elaziģ), East Anatolia (Muş) and Mediterranean (Adana). In order to assess damages in the epicenteral region, the information was gathered through Turkish Red Crescent representatives, local states, gendarmeries and the other security organizations in the cities.

These activities include preparing shelters for quake-victims, food procurement, blood granting services and social and mental support of hurts during the crisis. In the first day, Red Cross and Red Crescent launched the blood granting zones in hospitals. People were unsatisfied from Red Cross performance, but days later the situation improved and their satisfaction grew up.

Turkish Red Crescent also with contribution of the other groups and Red Cross, after surveying the crisis needs, prepared its proposal in declared it on 26 October.

Some 110 disaster expert from crisis management centers of Turkish cities and from the presidential institution branches, as well as 37 vehicles, volunteers and religious promoters, police forces and teachers with working ground of “the society leaders organizing” were being detached to the incident region. The Foundation for Human Rights and Freedoms and Humanitarian Relief (İHH; İnsan Hak ve Hürriyetleri ve İnsani Yardım Vakfı, Endowed Organization of human rights and liberties, ( 3 )) conveyed its team ( Fig. 1 ) before Sunday sunset there and started its operations to save people beneath debris.

İHH rescuer is looking for a survivor in Van ( 3 )

In 23 October, 2600 tents, 7500 blankets, 100 ovens and other means, namely sleeping bags, heater and food procured for the quake victims. Food procurement centers were held for whom lost houses, or having unsecure houses because of the possible aftershocks. Referring to near zero temperature at nights, the need for blanket and tent were of the high precedence.

Crisis response groups of Turkish Red Crescent established two tent camps in a stadium at Erciş County. Two hundred and sixty families settled down in these camps. Sufficient blankets and 118 heaters distributed in these two camps. Turkish Red Crescent was dispending warm food among people. The mobile kitchens were installed in location. Red Crescent food machines were dispending soup and tea among them as well ( 4 ). One month after the event (21 November 2011) the first author was told in Van food assistance center, about 120,000 peoples received warm food per day after the quake. In addition, two wind tents and two storage tents were established to adopt individuals and storing the helps. Another tent camp was pitched at the Van city center with the capacity of 232 tents ( 5 ). Food was sent from different sources including Van and the other provinces to the prone areas.

MOH warned people just to drink the mineral water because of the numerous cases of the diarrhea prevalence between populations ( 4 ).

Until 21 November, 18000 persons were fixed in 12-tent city in Erciş and Van. Turkish Red Crescent established four tent camps and two Mevlana house from which three camps and one house were in Erciş and one camp and one house in Van center. Moreover, distribution of tent and Mevlana house in the village residents continued. The Red Crescent settled down 50,547 tents and 2,348 Mevlana houses and prepared a shelter for 248,859 persons and planned a contract for 2,000 container house (having an area of 21m 2 equipped with bathroom, restroom and kitchen) for Van and Erciş. AFAD ordered building of 20,000 containers. Until November 30, 2711 containers were built, from which 2081 were installed ( 5 ).

A Turkish journalist exploited from his popularity to help those who lost their house in the quake, through Twitter social network, wanted 22000 of his fans to email him if they were ready to help, and he could attract enormous helps ( 6 ).

Ministry of Health activated SAKOM (Emergency and Crisis Coordination center of Turkish Hygiene Ministry) for the operational response to the event under supervision of the Vice Minister. The quake injured people received medical care in Van, Erciş and the other neighboring provinces. Relief medicine groups from Van and other provinces began their operations immediately after the quake in the region. MOH sent 6 air ambulances and 201 normal ambulances and prepared 1700 hospital beds in the Van surrounding cities at the first day of incident for the saved persons.

Public services

The local officials closed universities and schools for 3 days. The government demanded the private sector to prepare the cranes to pick up the debris and this sector replied to this request. Electricity and telephone lines, which been disrupted after the event, a day after, came back to the ordinary status ( 5 ).

An enormous loss was imposed to education and study during the quake. According to the official statistics, 65 teachers died and a large number injured. Many of schools also collapsed. Minister of education, Omer Dincher devoted a lot of his time to this issue and put it that the education should not been interrupted. He also exclaimed that his objective was to reestablish schools at November 14. Finally schools have reopened nearly two-and-a-half months after earthquake.

It was requested from the teachers who had returned to their cities to return to Van. The minister also suggested that it would not allow to the schools in which there was possibility of destruction until the time they will be reconstructed. He announced that an equip comprising of 29 engineer and architecture were sent to Van to determine the demolished schools. The schools to which those students would be sent also determined.

International aids

The Turkish government announced in 23 October that there is no need for international aids and it only accepted Iran and Azerbaijan, its neighboring countries. Nonetheless, by increasing the number of unsheltered people at under zero temperature, two days after the main shock, they accepted the help proposals from all countries. The government suggested that it needed the after emergency aids such as prefabricated houses, container and tent ( 7 ).

Iranian Red Crescent (IRC) detached its personnel to Turkey. All of the actions of this group were in complete coordination with Turkish Red Crescent. Because of the previous coordination of these two organizations, IRC could begin its operations spontaneously. As well as the group settled in Van, three relief teams of IRC were in preparedness stage on the border line of two countries. This group settled its base on Iran border. IRC prepared 3000 tents, 1500 blankets and 2500 precooked foods for the rescued people.

European International Federation office was in contact with Turkish Red Crescent from the beginning. It was in contact as well with the International Committee of Red Cross (ICRC) to coordinate the actions and activate the Recovery of Familial Links (RFL) in order to help the hurt families. The federation was cooperating with the other institutes and organizations involved in the humanitarian helps. These collaborations are in the first place crucial in preventing interference and overlapping of the helps, supplying the standard reply and guaranteeing the dignity of humanitarian actions commensurate with the needs of Turkish population. Austria, Belgium, Slovenia, France, England and Sweden procure more than 2300 winter tents in the first three hours of the incident. The other member countries of the civil support structures of Europe as well enunciated their readiness for the help. After the acceptance of the aids by Turkey, European Union dispatched its aid groups with a six-person team ( 9 ). In addition, Ireland sent 600 tents and 3000 blankets for the hurt people ( 3 ). Russia sent its aids including necessary goods and 214 tents with 37 tones weight ( 10 ). United States was the last country that proposed help and utilized its own planes on the European bases for the relief purposes ( 11 ). Japan granted enormous aids such as considerable number of tents for the hurts.

AmeriCares- an American organization- that previously trained a large number of Turkish medical rescuers detached its needed storage for curing of 15000 survived injured people from its goods store in Amsterdam at October 24 ( 11 ).

Humedica- a German organization- detached its medical team together with their equipment to the region for curing of 3000 people. This team arrived at October 24 there. Its American counterpart, OBI (Operation Blessing International) arrived at October 25 to Van and settled its field hospital in the local club of Erciş. This group dispensed two trucks loaded with mineral water, 3500 precooked foods and hygienic packages among 170 families living in the camp ( 12 ).

French NGO of borderless telecommunication (TSF; Télécoms Sans Frontières) as the only international NGO, despite of the rejection of the international aids by Turkish state, arrived in 24 hours at Van province and resided in Erciş and set up the telecommunication network and contributed Red Crescent in management of shelters. TSF provided the possibility of foreign contacts and exploiting Internet particularly for the refugees. This group mission ended at October 28 ( 12 ).

Moreover, United Nations High Committee for Refugees (UNHCR) contributed in occurred crisis through providing tent and blanket for quake hurts and especially Iranian and Afghan refugees, resident in Van and also via sending the specialized rescue force and exclaimed that the refugees of this region, generally from Iran and Afghanistan, are more vulnerable than indigenous people are ( 12 ).

Social and mental aftermaths

Psychologists and social services experts dispatched to the region to give the social aids, mental support for victims who lost their families, and whom diagnosed by post-traumatic stress disorders (PSTD). They exclaimed that among their patient, impacts caused by the event have created influences such as sorrow, anxiety, insomnia and reaction to partial noises. Doctors tried to solve these problems and particularly insomnia via medicines. Children suffered from mental disorders too. In such as these incidents, children depend on their mothers far more than other times and refrain from entering in the closed places. Waking up with repetitious nightmares, polyuria, sleep talking and fear of sleeping alone are the other symptoms seen in children that psychologists should cure. In these occasions, father, mother or other relatives should support the child at the first step, calm him/her and talk while playing with him/her.

Totally 155 children became orphan. The manager of Social Services Department of Van affirmed that those orphans would be under their support, the government would give their families pecuniary helps, they would not dissent from their families and they would be under supervision and retrieve psychological aids.

The cold weather provoked people stress and they were unsatisfied of unequally distribution of the aids. Such that they complained that: “despite the existence of the aids, but they were granted unfairly and by prejudice. In that circumstance in which they could not enjoy of the preparations and by considering the cold weather of the region in which there is fear of snow and rain every time, they are worry about death ( 13 ). After the quake, some holes were created with 10–15 meters length and several meters depth. Consequently, the rustics could not sleep comfortable and feared that the similar holes would form under their houses and they request from the officials to survey those holes ( 14 , 15 ).

Since the region were suffering from numerous aftershocks days after the main shock, many of them by magnitude more than 3, there was the probability of collapse of partially-damaged buildings or even the apparently safe and buildings. Therefore, people were not going to their houses. 50 hours after the main shock, an aftershock of M5.7 occurred and caused more damages.

Results of the Surveying: Disaster Management: Day per Day

The process of disaster management is studied herein in a day per day basis until 23 days after the main shock. It was aimed to follow up briefly the disaster management process, document the interventions and responses and qualifying it.

October 23, 2011

At 13:41 by the local time, the earthquake jolted East Turkey (Van province) for about 25 seconds. In its first account, Kandilli Observatory and Earthquake Research Institute (KOERI) in Istanbul announced the local magnitude (ML) as 6.6 and its epicenter to be at Tabanli village in the north of Van. This quake was felt in the cities of Diyarbakir, Ağri, Iģdir, Şirnak, Muş, Tunceli, Batman, Mardin, Erzurum, Bingöl, Bitlis, Siirt and Shanlıurfa regions. According to earliest reports, about 60 buildings were collapsed. Electricity and telephone communication were cut in Van and Erciş. In addition, some buildings in some of neighboring cities (Bitlis and Hakkari) were damaged. Problems in air transportation in, Ferid Melen airport of Van were reported, but except for the first hours (when the airport was declared temporarily out service and the flights were conducted to Erzurum airport), the airport continued action for service flights ( 5 ).

At the first hours after the main shock, 50 persons rescued from the debris, received initial cure at the hospital yard. Fire fighting groups started their actions. The Red Cross annunciated collapse of 25 flats and 1 dormitory. “Mujadele” newspaper web site reported immediately that the situation is good now and in the city center, no dead or damage is seen. Erzurum governor annunciated the detachment of a search and rescue group to Van. Turkish Red Cross moved towards the region to bring necessary tools such as blankets and tents. Turkish Prime Minister, R. T. Erduģan, revoked Monday (24 October 2011)session and went to Van. During the evening, homeless people faced the cold weather. The survey of the early response to the Van earthquake in the first day is as follows:

• 13:41- Occurrence of the quake with 7.2 magnitude 19 kilometers from Van.
• 14:30 – The first group from Turkish Red Crescent dispatched to region to survey (Turkish Red Crescent as other Red Cross Societies in the world is just responsible of preliminary medical relief, food dispersing and temporally and emergently settlement).
• 15:55 – Kandilli Observatory director, Professor Mustafa Erdik announced the magnitude to 7.2 (modifying from early announcement of M6.6).
• 16:08 – Kandilli Observatory annunciated the macroseismic intensity to be between VIII and IX Mercalli in the epicentral region.
• 16:32 – Kandilli Observatory, estimated the structural damages and imposed losses to be 3200 to 3400 buildings out of order, 600 buildings with sever damages, 50 buildings fully collapsed and deaths 500 through 700 persons.
• 16:42 – Reopening of Ferid Melen airport, (declared out of service at the time of the event). In the first 3 hours after the event planes went to Erzurum airport.
• 16:54 – A dormitory collapsed and fortunately has no death.
• 17:30 – According to initial affirmations, 30 dead and 156 injured were reported in Erciş.
• 19:57 – Rescue and search groups arrived at Van.
• 21:00 – Prisoners in Van prison takes the opportunity of opened doors and escaped!
• 21:10 – From 200 escaped prisoners, 50 surrender themselves after meeting their family.
• 21:30 – All of the National Red Cross Society and Turkish Red Crescent forces detached to the east for relief.

October 24, 2011

Totally 217 dead and 1090 injured were reported and 970 buildings collapsed. Natural gas, water, electricity and telephone systems, disconnected after event in Van, reinstalled after 24 hours.

Turkish government sent Urban Search and Rescue (USAR) forces and emergency medical team from 44 provinces and 37 different organizations with military and urban planes to the region. Three cargo military planes were responsible for transmitting equipment and persons from Ankara to Van full time and continuously and this was continued later days. USAR actions continued uninterruptedly. 1584 USAR personnel, 491 medical personnel and 10 USAR dogs worked on region, while 68 ambulances, 7 air ambulances, 256 loader trucks were used.

Turkish MOH settled two field hospitals in Van and Erciş. Turkish Disaster and Emergency Management Presidency, AFAD (which is an organization equivalent to Iranian Disaster Management Organization but in Turkey, it directed under the supervision of Prime Minister) dispatched equipment and rescue and save groups until 11 a.m. to the region. 2398 rescue groups went from 25 provinces to Van, comprising 680 nurses, 12 search and rescue dogs, 355 relief machinery, 7 air ambulances, 101 normal ambulances, 30 generators, 95 mobile toilet, 1719 kitchen sets, 3812 heater, 425 sleeping bags and 1 mobile oven ( 5 ). Turkish President and Prime Minister announced that they do not need international aids through Turkish Crisis and Emergency Management Broadcasting.

October 25, 2011

Military planes and two cargo planes (totally 37 planes) were sent to the region. In addition, 200 technical crew and 3 cargo military planes were ready to be sent to transmit subsidiary personnel and requirements. In order to cover the need for blanket and tent, five civil planes, three military planes worked to transmit the aids. A connection line set up between Ankara and Van. The requirements transmissions were continuing by cars. Ankara Esenboða, Istanbul Ataturk and Izmir Adnan Mendres airports employed noticeable number of their crew for transportation and transmission operations of the aids and people.

In general, 3346 search and rescue groups, 787 medical groups, 16 search dogs, 563 cranes and tractors, 138 ambulances from which 7 were aerial, 33 generator, 95 mobile toilets, 11211 tents, 25539 blankets, 1120 food packages, 513 heaters and 425 sleeping beds were sent. Search and rescue of peoples and first aids were uninterruptedly continued.

Although it was not appropriate season for construction, TOKI (TOPLU KONUT İDARESİ BAŞKANLIĞI; Turkey housing development administration) was ordered to rebuild the damaged buildings and finalize the half-constructed ones in one month so that people could reside there. The labors and farmers debts to Turkish National Bank postponed one year. Until the noon time of October 25, from 6 ruined buildings the rescue operations finished in three.

President Abdullah Gül canceled the Republic celebration ceremony due to the Van earthquake (29 th October) that is an official ceremony and holiday in Turkey. Turkish government gave positive answer to the international aids propositions, for which two days ago declared there is no need for such assistance ( 7 ).

In Van, some of Turkish Kurds stoned journalists and police forces in complaint against partially coverage of the disaster news by Turkish media ( 8 ).

October 26 2011

The confirmed number of death loss was declared to be 481 and 1650 injured. The number of aftershocks until 12:00 was 639 and the greatest aftershock was M5.7.

The Mayor of 34 th district of Van resigned because of the people complaint and their confrontation with Municipality workers. The Mayor himself acclaimed that the Municipality did not distribute aids and tents between people. The Mayor’s spokesperson told that people want tent, we have no authority, and the government does not collaborate with us. Therefore, we cannot persuade people that we have nothing and we resign. President Gül suggested that “we still do not need any help and, of course this does not mean the rejection of aids”. In response to the Israel proposition to help, he also emphasized that if they accept aids from other countries, they do not differentiate between them. He announced that he would travel to Van but did not determine date. He told that: “We would travel to Van, But in order not to form any obstacle in the progress of helps, this issue is under assessment”. Turkish Red Crescent formed National Pecuniary Aids Collecting Campaign and requested help from people and representative of International Red Crescent and Red Cross Societies ( 5 ).

October 27, 2011

The number of death declared to be 550. To meet the needs for tent and blanket in prone areas, five civilian planes, three military planes and totally eight planes were allocated to aids transmission. Terrestrial transportation continued as well.

After Turkey requested help, European Union responded immediately through preparing a six persons team of experts and 100 tents. According to the account of Prime Minister Office and in response to the Van province governor, 13 million TL (Turkish Lira) as the subvention was sent immediately.

Istanbul University set up an aids collection camp. In addition, its administrative and scientific employees delivered requirements such as blanket, hand-washing liquid, wet kerchief, battery, layette, dry milk and dry foods to a group of the Beyazit University to be reached to the students. The gathered goods via University rescue team were arrived to the villages around the region. Istanbul University also sent one 27 persons group to Van in order to technical survey. They should reside there until terminating of the search and rescue operations and should supervise and attend in reconstruction phase.

October 28, 2011

According to the account of the manager of Turkish Emergency and Crisis Management Organization (AFAD), up to 15:30 of October 28, the number of death was declared to be 575, and 2068 injured and 187 rescued people. As well as 8,710,000,000 TL subvention of state, 14,960,000,000 TL was the amount of gathered pecuniary aids. A transportation chain comprising of eight planes (5 civilian and 3 military) took the responsibility of aerial transmission of blanket ant tent towards hurt regions.

According to Kandilli Observatory, an aftershock of M4.5 occurred in Van. Turkish government announced that to prevent the reiteration of Van earthquake disaster, it would strengthen all of the buildings against quake with magnitude of nine throughout Turkey. In fact such declarations in the developing countries are mostly for public media usage, because the level of the great earthquake (Magnitude 9) is not experienced in Anatolian and Iranian shallow crustal earthquake history and the level of vulnerability in a country like Turkey is almost neglected in such histrionic declarations of the authorities!.

The authorities declared that in this project, all of the poor people houses will be reconstructed. Furthermore, all of the existing buildings in the city centers would be surveyed in terms of the strength and old ones would be reconstructed. Constructors announced that in this project, 9 million of obsolete buildings to be surveyed and to be reconstructed. Turkey has a seismic building code for construction of public buildings, but for the ordinary buildings, new regulations to be ratified. In this respect, all of the buildings with less resistance would be reconstructed.

Twenty-year house loan conveniences would be available to people and it will be tried to rebuild all of the non-resistant buildings.

October 29, 2011

Until 29 th October, the number of victims was declared to be 582 (of which 455 were in Erciş) and 4152 injured. From six ruined buildings in center of Van, the rescue operations ended in five of them. In one remained building six relief equips were still active. In Erciş, from 65 ruined buildings, operations ended in 58 and in the remaining ones, 26 groups with 150 personnel were still working.

The Deputy Prime Minister said that tomorrow night (at the end of 7 th night after the quake), search operation would end and disinfection operations would begin. He also wanted people to grant hot clothes to the people survived and lived in tents in the cold weather.

The gathered aids had been brought to a sugar factory in Erciş to be distributed. These aids include food, water, blanket and clothes. Five hundreds of 5 Litters water bottles were to be sold illegally that stopped based on reports coming from inhabitants and after the police reaction.

Turkish Minister of Urban Planning promised people lost their house to prepare the residential buildings of Van until September 2012 and while they were being constructed, the government would provide temporary shelters with prefabricated units for them ( 9 ). A comedian group from Istanbul went to Erciş to change the tragic ambiance of that city. This group held a birthday ceremony for a one-year old child.

October 30, 2101

The number of victims exceeded than 600. At night, the rescue groups terminated their work. It was set that since tomorrow, the disinfection operation begun.

According to Kandilli Observatory, an aftershock occurred at 03:55 with magnitude of M4.5 and its epicenter was Aşağı Gölalan village. This aftershock occurred with 5km depth. This aftershock followed by three other aftershocks having the magnitudes M2.5 to M2.7.

According to the direction of MOH and via Red Cross, a tent for drug distribution was settled in which 30 people were working and by presenting the doctor prescription, they received free drugs. Moreover, in a tent settled in the yard of one of the medical universities, psychologists gathered to help the quake victims having psychological injury. The local state exclaimed that it would employ 3000 persons for cleaning the debris and rubbles and supplying the social aids. This was an appropriate opportunity for temporary employment of workers who had been jobless due to the earthquake.

October 31, 2011

Eight hundreds new teachers dispatched in to Van by Ministry of education. The Minister also told that schools would be reopened until November 14 and the necessary measures for securing and reconstructing them have been taken.

Turkish Minister of Commerce and Customs, Hayati Yazici, exclaimed that all of foods, cloths, electronic instruments, stationery and hundreds of other tools existing in the customs would be sent for the quake hurts. In the first step, several tones of rice, sugar, oil, flour, conserved foods, clothes, shoes and washing substances would be sent to Van after precise laboratory control. In the whole winter, all of the discovered and seized goods and food materials would be sent via customs. He also said that prior to other works; the customs would pay attention to the aids received from foreign countries.

November 1, 2011

The list of sent items to the hurt regions announced as follows: 143 generator, 77 projector, 95 mobile toilet, 42711 tents (8166 from foreign aids), 54 public residence tents, 69 prefabricated houses, 160,360 blankets, 179,000 quilts, 37 mobile kitchens, 3051 kitchen sets and 5,792 sleeping bags. The Red Cross and the other rescue groups in tent towns (temporary residences) distributed warm food three times a day. In nine settled tent regions, the attempts to set up public telephones, laundries and other instruments were going on.

November 2, 2011

The Prime Minister, Erduģan, granted his one-month salary to the quake hurts. Many of the Parliament Representatives and Representatives of the Governing Party of Development and Equality Party in the Parliament ( Adalet ve Kalkınma Partisi; AK Parti) granted their salaries as well. Their subventions are excessive than 200,000 TL. The Prime Minister wanted the increment of Parliament Representatives to help quake victims. The other contributors were artists and representatives of other parties such as CHP, MHP, and AKP.

November 6, 2011

At 04:43 local time, another earthquake occurred with a M4.5 and its epicenter was located in Van Lake. It has not had any damage. In Van and Erciş, the quake victims held Qurban Fiesta and praying ceremony in the tents settled by Red Crescent and in undamaged mosques. The rescue groups and victims people greeted Qurban Fiesta to each other and gave thanks to the helps of the rescue groups. The Red Crescent rescue groups distributed fiesta food and gifts among people.

November 7, 2011

The Minister of Development visited the tents settled by Red Crescent in Qurban Fiesta. He visited as well a six-member family lived in a tent, listening their requests for immediate help to the family, in which two children and their father have been physically disabled.

November 9, 2011

According to the Kandilli Observatory, at 00:05 (midnight by local time) an important aftershock with a M5.5 occurred in Adilcevaz (closed to Van) with 4.3km depth. The Bayram Hotel in the Van City center collapsed. This hotel has been in service even after the earthquake and at that night was full of passengers, mostly the rescue workers and journalists, and was located at the south corner of Valiliģi square. In this hotel, 44 persons were killed among which there were three Iranian tradesmen and one Japanese relief force. During this aftershock, 20 buildings demolished, two of which were hotels. In general, about 100 persons were imprisoned under debris.

According to the recorded videos of CCTV’s, at the quake moment, electricity was disconnected and passenger running out from hotel. Two cars belonged to World News Agency, also parked in front of the Bayram hotel ( Fig. 2 ), one of them buried under the debris and became useless. From the other videos retrieved from the cameras throughout the city, whole city’s electricity was seen to be disconnected and separated slices of some buildings fell down on the ground.

Hotel Bayram of Van, before (down) and after (up) of its collapse in the aftershock of 9 November 2011, M5.6 ( 3 , 4 )

Given the primary reports, 25 buildings were damaged. The rescue operations performed in six regions of Van. Many of journalists resided in two damaged hotels; Bayram (which collapsed totally) and Aslan hotel. The number of survivors from these two hotels was 13 persons. Twenty-eight injured people rescued out of debris. Transportation of tent and blanket to the region was done using five military and two THY (Turkish airline) cargo planes. In addition, 260 of the region residents were translated to Istanbul and Ankara.

November 10, 2011

After demolishing of Bayram hotel, the angry inhabitants of Van gathered against hotel debris and demonstrated against Erduģan government and wanted Erduģan to resign. This protest ended by police intervention. Because of the explosion of pepper gas to disperse people, rescue groups get distance from the place inevitably and rescue operations were paused for a while.

November 14, 2011

According to Kandilli Observatory, three aftershocks occurred during half an hour: at 18:31 and 18:47; two of which with the magnitudes of M4.4 and M4.5 respectively, in Van Lake, and another one occurred at 18:54 with magnitude of M4.2 in the city of Muradiye (about 100km NE of VAN).

November 15, 2011

In the prone area 200 residential facilities were prepared for teachers. Four hundred prisoner of Van Tipi prison were sent to other prisons due to quake and the possibility of aftershocks. Most of prisoners were sent to the prisons in Black Sea coastal cities.

In Van earthquake by attending to damages extent and number of 644 deaths (of which 470 in Erciş) and also place of epicenter out of Van - about 30 km – and the time of the earthquake occurrence at 13:42 of weekend holiday (Sunday) ( 14 , 16 , 17 ), it seems that the extent of damages and casualties was limited for a country such as Turkey and an earthquake with such a magnitude (Mw7.2). According to the vulnerability of infrastructures in this country, the existence of ethnic tensions in Van province, and the location of the prone area in the most undeveloped eastern part of Turkey, and being away from the country’s developed section, the crisis was relatively well managed during and after the quake. After the event temporary shelters installed during a week and distribution of hygienic and alimentary requirements was made possible in 48 hours (People retrieving warm food were 120,000 in Van). These may relate to existence of Van airport and well equipped new hospital of Van, which have been inaugurated in September 2011, a month before the Van earthquake. Other positive point in disaster management in Van earthquake was the Turkish experiences in confrontation the natural disasters. The review of these achievements in the crisis management for our country, Iran, could be very important because of enormous similarity in cultural and economic issues, as well as the proximity of the two countries geographically and analogy in seismicity and vulnerability status particularly in North West of Iran and East of Turkey.

Ethical considerations

Ethical issues (Including plagiarism, Informed Consent, misconduct, data fabrication and/or falsification, double publication and/or submission, redundancy, etc) have been completely observed by the authors.

Acknowledgments

The assistance of the IIEES colleagues specially Dr’s E. Haghshenas and M. Bastami is greatly acknowledge for their useful assistance in the field studies and their helpful comment. The authors declare that there is no conflict of interest.

New disaster management system in Turkey: A case study of the 2011 Van earthquake

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Source mechanism of the 23 October, 2011, Van (Turkey) earthquake ( M w = 7.1) and aftershocks with its tectonic implications

• T. Serkan Irmak 1 ,
• Bülent Doğan 2 &
• Ahmet Karakaş 2  

Earth, Planets and Space volume  64 ,  pages 991–1003 ( 2012 ) Cite this article

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This study has investigated the rupture process of the 23 October, 2011, Van (Turkey) earthquake ( M w = 7.1) by using inversion of teleseismic waveform analysis and its tectonic implications. Focal parameters of the main shock and 21 aftershocks were obtained by using the first motion polarities of regional P -waves. The first results for the source rupture process were derived from broadband teleseismic P -waves. The main outcomes of the analysis are: (a) the main rupture is located around the initial break point, and the maximum slip amount was 3.6 m; (b) the size of the main fault plane area was about 40 km in length and 20 km in width, the duration of rupture was approximately 19 seconds and the seismic moment of the earthquake was estimated to be 5.53 × 10 19 N m ( M w = 7.1); (c) the rupture gradually expanded near the hypocenter and propagated both northeast and southwest, but mainly to the southwest. Tectonic implications of the earthquake were defined by field observations. The 23 October, 2011, Van earthquake occurred on a main thrust fault plane trending NE-SW between Lake Van and Lake Erçek located in the East Anatolian compressional province. This main fault plane and the secondary structural elements were generated by a continental-continental collision taking place in a region located 200 km north of the the Bitlis-Zagros Suture Zone.

1. Introduction

A destructive earthquake occurred on 23 October, 2011, at 10:41 (UTC) in Van, located in the east of Turkey (Fig. 1 ). The hypocenter determined by the Kandilli Observatory and Earthquake Research Institute (KOERI) is located at 38.7578N, 43.3602E, with a 15-km depth (KOERI, 2011 ). A total of 604 people were killed and more than 2500 people were injured, mainly by the collapse of buildings. A detailed earthquake report has been published by the Disaster and Emergency Management Presidency of Prime Ministry of Republic of Turkey (DEMP, 2011 ).

(a) The general neotectonic map of Anatolia. K—Karlıova, KM—Kahramanmaraş, DSFZ—Dead Sea Fault Zone, EAFZ—East Anatolian Fault Zone, NAFZ—North Anatolian Fault Zone (Şengör et al. , 1985 ; Barka, 1992 ; Bozkurt, 2001 ). (b) Neotectonic map of the East Anatolian and Van region. A—Ağrı Mountain, K—Karacadağ, N—Nemrut Mountain, S—Süphan Mountain, T—Tendürek Mountain, AF—Ağrı Fault, BF—Bulanık Fault, ÇF—Çaldıran Fault, EF—Erciş Fault, HF—Horasan Fault, IF—Iğdır Fault, MF—Malazgirt Fault, OF—Ovacık Fault, SF—Süphan Fault, BFZ—Balıklı-lake Fault Zone, BsF—Başkale Fault, ÇFZ—Çobandede Fault Zone, DFZ—Dumlu Fault Zone, HFZ—Hasan Timur Fault Zone, KBF—Kavakbaşı Fault, KFZ—Kağızman Fault Zone, DBFZ—Doğubeyazıt Fault Zone, KyFZ—Karayazı Fault, TFZ—Tutak Fault Zone, YSFZ—Yüksekova-Şemdinli Fault Zone, NEAFZ—Northeast Anatolian Fault Zone (Bozkurt, 2001 ).

The tectonic setting of Turkey and east Anatolia is the main factor in earthquake occurrence. The movement of the Arabia plate towards the Eurasia plate occurring along the Bitlis-Zagros Suture Zone (BZSZ) has been continuing from Serravalien (~12 Ma) to the present (Fig. 1(a) ). This time interval is called the Neotectonic period for the East Anatolia region (Şengör and Yılmaz, 1981 ; Dewey et al. , 1986 ; Koçyiğit et al. , 2001 ). The movement rate of the Arabia plate towards the Eurasia plate is about 20–30 mm/year according to GPS measurements (Reilinger et al. , 2006 ). The effects of the continental-continental collision in East Anatolia prolongs to the north of the BZSZ, as E-W slicing thrusts (Şaroğlu and Yılmaz, 1986 ). The collision created by the N-S movement of two continental crusts developed some structural elements related to the collision in the East Anatolian plate. The most important ones are the North Anatolian Fault Zone (NAFZ) and the East Anatolian Fault Zone (EAFZ) (Fig. 1(a) ). Besides, the impacts of the collision are observed as inter-continental synthetic back thrust faults, right and left strike-slip faults located in a region extending from the BZSZ to approximately 200 km north of the BZSZ (Şengör et al. , 1985 ). Additionally, the secondary tensional cracks and normal faults parallel, or at an angle, to the reverse faults developed during the thickening of the crust as a result of the collision of the continental plates. Similar features has been presented by Friedrich ( 1993 ) and Yin et al. ( 2008 ).

The Eastern Anatolia region, where all of these structural elements are observed, is defined as a compression region (Şengör and Kidd, 1979 ; Yılmaz et al. , 1987 ; Yılmaz, 1990 ). The Lake Van Basin which is a ramp basin developed as a result of the activities of the thrust faults in the Eastern Anatolia compression region includes secondary normal faults and strike-slip faults (Şengör et al. , 1985 ; Bozkurt, 2001 ; Koçyiğit et al. , 2001 ; Fig. 1(b) ).

The earthquake area is known as a seismically-active region and is classified as a first category seismic zone in which damaging earthquakes occur (Lahn, 1949 ). The seismicity catalogue for the area was reported to be incomplete, particularly with regard to seismicity of a magnitude M < 4, because of the absence or scarcity of seismic recording stations in Eastern Turkey (Turkelli et al. , 2003 ). Furthermore, historical and instrumental seismicity records prove that the area has produced a number of earthquakes from moderate to large magnitudes (Table 1 ).

The purpose of this study is to define the tectonic system that has deformed the region by using the surface rupture data, and fault plane solutions of the main shock and aftershocks of the 23 October, 2011, Van earthquake that occurred in the eastern Anatolian compression region. The source rupture processes of this earthquake were analyzed using teleseismic P -waves collected by the Data Management Center of the Incorporated Research Institutions for Seismology (IRIS-DMC). The source parameters of the 21 aftershocks (3.5 < M < 5.7) have been derived by using the first motion polarities of regional P -waves collected by KOERI. The fault plane solutions of the earthquakes that occurred in the seismogenic zone of the continental crust were carried out in detail. The results of the fault plane solutions were compared with the surface rupture geometry to reveal the active tectonic model of the Lake Van Basin.

2. Field Observations

The Van earthquake resulted in a main surface rupture (MSR), along with secondary surface ruptures, in an area extending in a N-S direction from Erciş to Van and extending in an E-W direction from Bardakçı Village to 4.5 km south east of Aşıt Village, and around the western shore of Lake Erçek (Fig. 2 ). The MSR was accompanied with left-lateral tensional cracking, developed following the compression, with less than 300 m laterally (Doğan et al. , 2011 ).

The fault plane solutions of the main shock and 21 aftershocks of the Van earthquake with the surface ruptures which occurred during the earthquake, A: Alaköy, B: Bardakçı, Ko: Kolsatan, K: Kozluca, Y: Yalnızağaç, S: Satıbey, As: Aşıt, Gu: Gülsünler, Go: Göllü, To: Topaktaş, T: Tabanlı, Vo: Van organized industrial site. G: Gedikbulak, Tr: Topaktaş road, U: United States Geological Survey (USGS), D: Disaster and Emergency Management Presidency of Turkey (DEMP), E: European Mediterranean Seismological Centre (EMSC), K: Kandilli Observatory and Earthquake Research Institute (KOERI). Focal mechanisms reported by different agencies for the mainshock (event no. 1) are also shown on the top of the figure (GFZ: Deutsches GeoForschungsZentrum, Germany; INGV: Istituto Nazionale di Geofisica and Vulcanologia; HRV: Harvard University; USGS: United States Geological Survey. The ruptured parts are shown with the straight lines and unruptured parts are shown with the dashed lines, the numbers on the map and above the focal mechanism indicate events given in Table 3 ).

The MSR of the Van earthquake was caused by a main fault that has a dominant thrust offset accompanied by minor left-lateral offsets in various locations (Fig. 3(a) ). When the north dipping plane, obtained from the focal mechanism solutions of the main shock by various international earthquake centers, is considered as the main plane, a minor left lateral is noticeable. The field observations of the MSR supported this focal mechanism solution. The overall strike of the MSR changes from N55°E to N70°E. This thrust fault is the primary fault plane with N60°E/65°NW strike and dip starting in Bardakcçı Village, located east of Lake Van on land. The strike of the MSR is N60°–65°E from Bardakcı Village to the Van-Erciş Highway with no change in dip direction and dip angle (Fig. 3(b) ). The MSR follows N65°– 70°E in the east of the Van-Erciş Highway and is observed with minor left-lateral offset in 200-m zones from north to south in the Van organized industrial site. The total length of the MSR (between Bardakcşi and east of the Van-Erciş Highway) is about 8 km with a 0.15-m maximum thrust vertical offset and a 0.09-m left-lateral offset. The MSR is not observed beyond 4.5 km southeast of Aşıt Village further east.

(a) A view of left-lateral offset on a concrete block, caused by the MSR. (b) A view from the main surface rupture (MSR) on the Topaktaş road. The vertical thrust offset is approximately 0.1 m. (c) The NE-SW trending, left-lateral strike-slip fault surface rupture with transpressional component (push-up structures) on the west side of Lake Erçek. (d) The en-echelon shaped tensional cracks in Erciş. (e) View of the landslide and liquefactions near Topaktasş village.

Another surface rupture of 4-km length, located between Kozluca and Yalnızağaç villages in the west of Lake Erçek, indicates a right step-over transpressional left-lateral strike-slip fault geometry (Fig. 3(c) ). The strike of the second fault varies N-S and N15°E. It was mainly followed in fields and grasslands, so the left-lateral offset was only measured as 0.08 m at one location in the village of Yalnızağaç. This fault caused rockfalls at the northwest of Lake Erçek and does not continue northeast of the lake. In addition, triangular facets extending in a N-S direction and left-lateral offsets in the E-W ridges-valleys were observed between high rugged morphology and low plain morphology between the villages of Satıbey and Kolsatan.

Several secondary structural features of the region are observed in the northern block of the main fault. These features are seen in Erciş, and the villages of Gülsünler and Göllü, located around the Van-Erciş Highway. These secondary structural features were observed in Erciş with a N10°–40°E direction as en-echelon tensional ground cracks with a maximum 2-m zone (Fig. 3(d) ). The maximum vertical offset was 0.3 m. Although the rupturing plane was not circular, down blocks were back-tilted to the rupturing plane. This surface rupture geometry is observed discontinuously in an east-west direction between the villages of Gülsünler and Göllü. The southern blocks, which moved downward, were observed along the secondary surface ruptures. The same type ruptures had been observed in a delta located in Gölcük-Kavaklı near the western fault end of the 1999 Kocaeli (Turkey) earthquake, and was defined as the Kavaklı normal fault (Barka et al. , 2002 ). In addition to the secondary surface ruptures, landslides and liquefactions were widely observed in the northern block of the region (Fig. 3(e) ).

3. Seismological Data Base

The number of digital broadband stations operated by The National Earthquake Monitoring Center of the Kandilli Observatory and Earthquake Research Institute (NEMC-KOERI) has been increasing since the devastating earthquake of 17 August, 1999, in Turkey. Therefore, it is possible to obtain reliable fault plane solutions for any area of Turkey, using either conventional methods such as first motion polarities or using waveform inversion techniques. Broadband data with vertical components of teleseismic P -waves were retrieved from the Data Management Center of the Incorporated Research Institutions for Seismology (IRIS), selecting 35 stations with epicentral distances between 30° and 100° (Fig. 4 ). The data windowed at 50 seconds starting at 10 seconds before P -wave arrival and was integrated to displacement, and band-pass filtered between 0.002 Hz and 1.0 Hz. Figure 5 shows the depth of the seismogenic zone for the region, using the aftershocks ( M > 2.0) which occurred within ten days of the main-shock. The data set was obtained from the KOERI catalog ( http://www.koeri.boun.edu.tr/scripts/Sondepremler.asp ).

Station locations used for the focal mechanism (right) and the slip distribution analysis (left). The yellow star indicates the epicenter, and the triangles are the stations used for the relocation of the analyzed aftershocks (red triangles are used for the first motion solution of the mainshock).

Distributions of the 23 October, 2011, Van earthquake (main shock shown by the red star) aftershocks and their depths.

4. Focal Parameters of the Main Shock and Aftershocks

The fault plane solutions were calculated by utilizing P -polarities running the focmec programs (Snoke et al. , 1984 ) for the mainshock and 21 aftershocks of the 23 October, 2011, Van earthquake. All available polarities from national seismic stations were carefully considered. The number of stations with unambiguous first arrival polarities varies from earthquake to earthquake, but events with fewer than 10 clear polarity readings were discarded, as were those with ambiguous polarities. The takeoff angles were calculated according to the same velocity structure used for the determined location (Table 2 ). The possible nodal planes which agree with the first motion polarities were searched, running the focmec program (Snoke et al. , 1984 ). The P -waves were converted to displacement in order to see the P -wave onsets better due to a low S/N ratio. Assuming the double-couple model for the seismic point source, P -polarities on displacement seismograms were then read. Polarity errors could be caused by low S/N ratio at stations near nodal planes, so called ‘mislocations’, or structural heterogeneity, biasing calculation of azimuth and take off angle and aliasing effects (Scherbaum, 1994 ). However, no polarity error was allowed in the solutions. Events with multiple acceptable solutions, indicating different mechanisms, or with faulting parameter uncertainties exceeding 20°, were not included in this study. The studied aftershocks have been re-located using digital broadband records. The epicenter coordinates of the after-shocks given by KOERI were preliminary, so the P - and S -wave phases were re-read to reduce the horizontal (ERH) and depth (ERZ) error. We calculated hypocenter locations by using P -wave arrival times of at least ten stations and also the S -wave arrival times of at least two stations. The aftershocks were processed using HYPO71 (Lee and Valdes, 1985 ) for the hypocenter determination. However, 1–2-km differences were obtained between the first solutions and ERH and ERZ. The digital data and error values are available http://barbar.koeri.boun.edu.tr/sismo/zKDRS/zzTReventIndex.asp for the preliminary results.

The first motion polarity solution of the mainshock represents the initial movement at the focus, whereas the moment tensor solution represents the source parameters of the large slip area. This explains the difference between our first motion solution and moment tensor solutions reported by different agencies. When the fault plane solutions with tensor analysis issued by other institutions are plotted on the sphere, including the stations utilized for the first motion polarity analysis, it is clear that they could not precisely distinguish the compression and dilatation (Fig. 6 ). Therefore, the fault plane solutions that were obtained by the first motion polarity analysis represent the rupture initiation better than the moment tensor analysis. However, the fault model based on the moment tensor solution is more appropriate than the fault model estimated from the focal mechanism by the initial P -wave polarity, since the focal mechanism by the P -wave polarities represents only the initial rupture process during the mainshock. Thus, the focal mechanisms obtained by the moment tensor solution in the inversion method were used. Indeed, several source inversion studies, using teleseismic data, assumed fault models based on moment tensor solutions (e.g. Kikuchi et al. , 2000 ; Yagi, 2004 ; Yagi et al , 2004 ).

Focal mechanism of the main shock obtained by P -wave first motion and moment tensor analysis, and results published by other institutes (see Fig. 2 for abbreviations).

In addition, the fault plane solutions were compared with the surface ruptures mapped in the field. The strike-slip faults along with the thrust faults that were also determined by the fault plane solutions of the aftershocks, and tensional cracks possibly related to the normal or left-lateral strike-slip faults, were observed especially in the overlapping northern block due to the NW-SE compression among the micro-scaled continental plates. A similar fault plane solution pattern was observed in the 1952 Kern county earthquake which occurred on the Pleito thrust fault in the north of the San-Andreas fault, which presented both normal and thrust faults with a strike-slip offset component (Webb and Kanamori, 1985 ).

5. Teleseismic Waveform Analysis of the Main Shock

To determine the focal mechanisms for the 23 October, 2011, Van earthquake from teleseismic broadband data, we introduced a time-domain iterative inversion method developed by Kikuchi and Kanamori ( 1991 ). We chose 35 stations and picked up vertical P -waves for the analysis. The azimuthal coverage is good enough to resolve the focal mechanism and also some details of the momentrelease distribution. With the approximation of a single point source, we determined the fault mechanism so that predicted waveforms best fit the observed ones (Fig. 7(c) ). We used teleseismic broadband P -wave data recorded at IRIS-DMC stations retrieved via internet. The data were band-passed between 0.01–0.5 Hz using a zero phase-shift Butterworth band-pass filter to remove long-period drift and high-frequency noise, then the data was converted to a ground displacement with a sampling interval of 0.2 s.

Focal mechanism obtained using the Kikuchi and Kanamori ( 1991 ) method, (a) source time function, (b) obtained focal mechanism, (c) waveform fitting. The upper seismograms are observed and the lower seismograms are calculated. The number above the station code is the peak-to-peak amplitude of the observed waveforms (micro-meter) and the numbers below indicate the azimuths of the stations.

The Green’s functions have been computed using the Kikuchi and Kanamori ( 1991 ) method. The ray is incident almost perpendicularly on the receiver at teleseismic distances, and is not affected by near source crustal effects, so we used a standard JB crustal model to compute the theoretical waveforms. A Q filter was used with the attenuation time constant t p = 1 s for P -waves and t s = 4 s for S -waves. The moment tensor solution indicate that the 23 October, 2011, Van earthquake has a reverse faulting mechanism with a small amount of left-lateral strike-slip component (Fig. 7(b) ).

To obtain the slip distribution, a single fault plane was assumed for the waveform analysis. The initial size of the fault plane was taken to be 75 km × 25 km from the aftershock distribution, and the rupture was assumed to start at the hypocenter of the mainshock. According to the right-hand rule, the strike and dip angle-directions were assumed to be 246° and 46°NW respectively, referring to the moment tensor solution obtained in this study.

Theoretical Green’s functions were computed for simple layers and were referred to the Jeffreys-Bullen model, using Kikuchi and Kanamori’s ( 1991 ) method for all stations; this is due to the fact that it is generally expected that the observed seismograms are less affected by local site effects in the teleseismic range. The spatiotemporal distribution of slip on the fault plane was inverted by the teleseismic body-wave inversion program developed by Yoshida et al. ( 1996 ) and Yagi and Kikuchi ( 2000 ). For discretization in space, the fault plane was divided into 15 in the strike direction and into 5 in the down-dip direction (making a total of 75 subfaults with an area of 5 km × 5 km). The slip rate function of each subfault is expanded into a series of 2 triangle functions with a rise time of 1.0 seconds. The rupture front velocity of 3.0 km/s was selected by trial and error, which determines the initiation time of the basis function at each subfault, that minimizes the residuals between the observed and predicted waveforms. To suppress instability or excessive complexity, a smoothing constraint was applied to differences in the moment release.

The results for the slip distribution obtained by teleseismic waveform inversion are shown in Fig. 8 . Figure 9 shows the observed and predicted waveforms. The overall matching between the predicted and observed waveforms is very good. The total seismic moment is calculated as 5.53 × 10 19 N m ( M w = 7.1), similar to the seismic moment of 5.8 × 10 19 N m derived by the Deutsches GeoForschungsZentrum, Germany-GFZ, 6.40 × 10 19 N m calculated by KOERI, 7.1 × 10 19 N m calculated by HRV, and 5.6 × 10 19 N m calculated by USGS ( http://www.emsc-csem.org/Earthquake/tensors.php?id=239856&id2=cz772;INFO ). The main rupture is located around the initial break point and the maximum slip is 3.6 m, if the shear modulus is assumed to be 30 GPa. The size of the main fault was about 40 km in length and 20 km in width, and the duration of rupture was about 19 seconds with M w = 7.1. The average stress drop Δ σ = 6.1 MPa is comparable to a typical stress drop value of 3 MPa for inter-plate earthquakes (Kanamori and Anderson, 1975 ).

Slip model from inversion of teleseismic waves: (a) focal mechanism, (b) moment rate function, (c) map view of the slip distribution (white circles indicate the aftershocks recorded within the first 24 hours), (d) slip distribution on the fault. The white star indicates the focus.

P -wave waveform fits for the inversion, with observed and calculated waveforms shown as black and red lines, respectively. The number below the station code is the peak-to-peak amplitude of the observed waveforms (micro-meter). The numbers above indicate the distance and azimuth of the station, respectively. The arrows correspond to a small peak that occurred in the moment-rate function after about 15 s.

In the total slip distribution, a large asperity area can be seen with a large slip in the hypocentral area of the fault plane. The rupture is very smooth and gradually expands near the hypocenter and propagates bilaterally in the directions northeast and southwest (but mainly to the southwest). The main moment release areas are located at and around the hypocenter. The rupture front also reached a shallower part of the fault plane (asperity area) about 9 seconds after the rupture initiation. In the moment-rate function, a small peak occurs after about 15 s. This peak is due to asperity in the lower corner of the fault plane (Fig. 8(d) ). In some broadband seismograms presented in Fig. 9 , this peak is recognizable, too. According to these results, an asperity was broken at 15 s after the focal time of the main shock at a distance of about 40 km away from the hypocenter. A barrier with higher stress (or lower stress) and with a width of about 15 km was located between the asperity and the main slip area. The rupture jumped over this barrier with a velocity comparable to the rupture velocity.

The distribution of the slip vectors indicates that a thrust fault mechanism with a small left-lateral strike-slip component (assuming the NE-SW plane is the active plane) occurred near the hypocenter and in deep parts. However, a small left lateral strike-slip is dominant in shallow parts of the fault plane mainly NE of the epicenter. The moment release and displacements rates in the shallower parts of the fault plane are smaller than the deeper parts of the fault plane. This situation could reduce the chances of a continuous surface rupture. If the rupturing of the fault plane reached the surface, the left-lateral strike-slip component could be mainly seen at the northeast of the main fault.

6. Tectonic Model and Interpretations

The ophiolitic rocks emplaced to the Lake Van Basin along the thrust planes during the Paleotectonic period (before Neogene) constituted the rugged mountainous morphology in the region (Yılmaz et al. , 1993 ; Parlak et al. , 2000 ). This continental-continental collision type plate motion creates thrust faults with lengths less than the length of the BZSZ. Continuation of the compression during the Neotectonic period in the region developed several folds and thrust faults in the Neogene and Quaternary units deposited in the Lake Van Basin.

The thrust faults in the Lake Van Basin have the potential to produce earthquakes with magnitude greater than six. The thrust faults cut the Plio-Quaternary deposits especially in the north of Van city center (Örçen et al. , 2004 ). Thereby, these faults are likely to be active. Additionally, the minimum length of these faults is about 10 km, so each of these faults has the potential to generate an earthquake of magnitude greater than six ( M > 6) (Wells and Coppersmith, 1994 ). One of the thrust faults, which has a fault plane dipping towards the NW, ruptured in the Van Lake Basin and created the Van earthquake. This rupture, which took place along the intra-continental thrust fault, developed secondary structural features such as left-lateral strike-slip faults with transpressional component and tensional cracks. The reason for this is that the widening areas related to the NE-SW left-lateral faulting could occur as a result of the NW-SE compression of the region. The fault-plane solutions of the main shock and the field observations proved that the 23 October, 2011, Van earthquake was generated by an intra-plate thrust fault with a NE strike and NW dip. Additionally, the rupture of this fault plane developed the secondary faults and created the aftershocks and several tensional cracks on the ground surface or beneath the ground surface.

7. Conclusion and Discussions

This study has investigated the rupture process of the 23 October, 2011, Van (Turkey) earthquake by the inversion of teleseismic waveform analysis and its tectonic implications. The teleseismic data set does not provide details of the slip distribution, but it provides the same general characteristics as other data sets such as near field, or strong ground-motion, data (Hartzell and Heaton, 1983 ; Yagi et al. , 2004 ). Therefore, we discuss the general features of the rupture process and compare the focal mechanisms of the analyzed earthquakes with field observations.

The initiation of rupture is usually described by the first motion polarity solution. However, the rupture direction could change during large earthquakes. The entire rupturing is modeled by slip-distribution modeling, which models the waveform. Therefore, the moment tensor solution is more suitable than the first motion polarity solution in terms of representing the entire rupturing process. Additionally, the strikes of the fault planes obtained from the moment tensor solutions are more consistent with the main surface rupture. The difference between the directions of the fault planes obtained from the first motion polarity solution and the moment tensor solution indicates that the direction of the rupture initiation is different from the entire rupture propagation.

The inverted source process model shows that a large asperity was located on the hypocentral area on the fault plane; with a maximum slip about 3.6 m. The rupture was very smooth and gradually expanded near the hypocenter and propagated bilaterally in the direction of northeast and southwest, but mainly to the southwest. The rupture process of the 23 October, 2011, Van earthquake is characterized by a smooth and bilateral rupture.

The aftershocks in the region are accumulated between the villages of Gedikbulak and Alaköy and have a NE-SW spread (see Fig. 2 ). The majority of the aftershocks occurred on the overlapping northern block and on or around the main thrust fault plane (Fig. 10 ). The main faulting plane of the entire faulting process could be located under the surface, while the surface ruptures continue east of the study area. The majority of the aftershocks investigated in this study have a strike-slip component, but the dominant component of the MSR is thrust. The normal and thrust aftershocks are related to the rupturing of the secondary faults created by the NW-SE compression, especially in the northern block. The Van earthquake was a result of the rupturing of a main thrust fault plane in the NE direction and with a 58°NW dip. This rupturing caused secondary intra-plate tensional cracks, left-lateral strike-slip faults on the northern block and a secondary right-lateral strike-slip fault with E-W direction obtained from the fault plane solution of the aftershock numbered 22 in Table 3 , on the southern block. Both right-lateral and left-lateral strike-slip faults can develop in pure compressional areas (Philip et al. , 1989 ). However, some of those faults could be unobservable on the surface. The fault plane solution of the aftershock numbered 22 is an example of this.

Main shock slip distribution and analyzed aftershocks with the MSR (the numbers indicate the events given in Table 3 , see Fig. 2 for symbols and abbreviations).

The surface ruptures observed from Erciş to Alaköy located on the northern block of the main thrust fault were defined as tensional cracks. These surface ruptures could be the structural products of a transtensional left-lateral strike-slip fault, and is an indication of intra crust deformation and suits with the direction of the aftershock pattern. The origin of the tensional cracks observed in the region could be explained by either normal faults or transtensional components, especially of left-lateral strike-slip faults. Both fault types are secondary and “intra-plate” with limited lateral continuation. In other words, the activities of these faults are directly related to the rupturing of the thrust faults in the region. In some regions of the world, there are several examples of both normal and strike-slip faults which developed due to a N-S compression of the region. For example, normal faults that were parallel and semi-parallel to the strike of the Vergent thrust fault System (WTS) developed during the 4 July, 2001, earthquake in the Altiplano region of north Chili in the overlapping continental plate (Somoza, 1998 ; Farias et al. , 2005 ). In addition, it was indicated that the normal faults could be transtensional faults that created the pull-apart basins in the same region (David et al. , 2002 ). Another example is that several normal faults parallel and semi-parallel to the thrust faults in the north and northeast of the Alborian Basin in Spain developed contemporarily with the overthrust (Roca et al. , 2006 ). Additionally, a graben was formed by the normal faults parallel to the reverse faults of the continental thrust zone and strike-slip faults developed concurrently due to regional compression in the West Europe Carpathian region. Although the reverse faults were dominant in the southeast of the East Carpathian region, normal faults with the same strike were observed in the northeast region (Oszczypko et al. , 2006 ; Picha, 2011 ). The small-scale normal faults parallel to the reverse fault planes that occurred along with the raising of the hanging wall, and shortening, were determined by the tectonic model of the 2008 Wenchuan earthquake in the Tibet Plateau (China) (You-Li et al. , 2010 ). These normal faults developed as a consequence of both heterogenic stress distribution in the seismogenic zone and thickening and shortening of the overlapping block.

The surface appearances of the normal faults based on the fault plane solutions of the aftershocks are in the form of tensional ground cracks in the study area. These tensional cracks are the secondary structural features developed on the overlapping northern block. The development of the tensional cracks are either related to the normal faults created by the thickening and contraction of the northern block, or the rupturing of the transtensional parts of the intra-continental strike-slip faults created by the compression.

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Acknowledgements

We would like to thank the Rector of Kocaeli University, Prof. Dr. Sezer Ş. Komsuoğlu, and the retired dean of the Engineering Faculty, Prof. Dr. Savaş Ayberk, and Prof. Dr. Mithat Fırat Özer, for their support, and the Rector of Van 100. Yıl University, Prof. Dr. Peyami Battal, for providing us transportation and accommodation during our stay in Van. Also, a special thanks is extended to Assistant Prof. Dr. Özkan Coruk for his contribution during the office work and Serdal Karaağaç for his contributions during the field and office works, and John Pyle for his reviewing effort. We also thank two anonymous reviewers for their helpful comments that improved the manuscript.

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Irmak, T.S., Doğan, B. & Karakaş, A. Source mechanism of the 23 October, 2011, Van (Turkey) earthquake ( M w = 7.1) and aftershocks with its tectonic implications. Earth Planet Sp 64 , 991–1003 (2012). https://doi.org/10.5047/eps.2012.05.002

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Received : 19 December 2011

Revised : 18 April 2012

Accepted : 05 May 2012

Published : 26 November 2012

Issue Date : November 2012

DOI : https://doi.org/10.5047/eps.2012.05.002

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• Source rupture process
• East Anatolian compressional province
• Van earthquake
• thrust fault
• focal parameters

• DOI: 10.2495/SC131182
• Corpus ID: 129427966

New disaster management system in Turkey: a case study of the 2011 Van earthquake

• F. Oktay , C. Tetik , +1 author G. Cebi
• Published 3 December 2013
• Environmental Science, Engineering

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Introduction, section snippets, references (48), cited by (28).

Tectonophysics

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On the basis of independent GPS data, the performance of the single slip model in this study is an improvement on that of the two-fault model determined by Elliott et al. (2013). Altiner et al. (2013) also gave a simple single-fault slip solution with a maximum slip of 4 m under the constraints of limited far-field GPS measurements. Because GPS observations are too distant from the fault and sparse to accurately determine the fault location and slip pattern, their slip model was not compared here.

GNSS cors network of the University of Palermo: Design and first analysis of data

A new high-resolution pollen sequence at lake van, turkey: insights into penultimate interglacial-glacial climate change on vegetation history, seismotectonics and rupture process of the m<inf>w</inf> 7.1 2011 van reverse-faulting earthquake, eastern turkey, and implications for hazard in regions of distributed shortening, ground motion simulations for the 23 october 2011 van, eastern turkey earthquake using stochastic finite fault approach.

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2023 Turkey Syria Earthquake Case Study

AQA GCSE Geography > The Challenge of Natural Hazards > 2023 Turkey Syria Earthquake Case Study

When and where did the 2023 Turkey-Syria earthquake happen?

At 4.17 AM on February 6, 2023, a powerful earthquake struck southern Turkey and northern Syria. The epicentre was located 37km (23 miles) west-northwest of the town of Gaziantep in Turkey, close to the border with Syria. The earthquake registered a magnitude of 7.8, making it one of the most devastating earthquakes in the region in recent history.

A map to show the location of the Turkey Syria earthquake

Background on the Level of Economic Development

Turkey and Syria have differing levels of economic development :

• Turkey: Turkey is classified as an upper-middle-income country ( newly emerging economy – NEE) with a diverse economy with strong industrial and agricultural sectors. Despite regional disparities, it has a relatively well-developed infrastructure and emergency response capabilities.
• Syria: Syria, on the other hand, is classified as a low-income country (LIC), especially after more than a decade of civil war that has severely damaged its infrastructure, economy, and social services. The ongoing conflict has left many areas in dire conditions, with limited capacity to respond to natural disasters. Before the civil war, Syria was a middle-income country (NEE).

What caused the Turkey-Syria earthquake?

The 2023 Turkey-Syria earthquake was caused by tectonic activity along the East Anatolian Fault, a major fault line that runs across southeastern Turkey. The East Anatolian Fault is a strike-slip fault where the Anatolian and Arabian Plate slide past each other horizontally. Strike-slip faults along plate boundaries are known as transform or conservative plate margins. The earthquake occurred due to the sudden stress release built up along this fault line over time. This movement caused a rupture in the Earth’s crust , releasing massive energy and resulting in severe ground shaking. The region’s complex geology, with multiple interacting fault lines, contributes to its high seismicity.

Conservative Margin Turkey Syria

What were the primary effects of the Turkey-Syria earthquake?

The primary effects of the 2023 Turkey-Syria earthquake were catastrophic:

• Building Collapse: Thousands of buildings, including homes, schools, and hospitals, collapsed. In Turkey, cities like Gaziantep and Kahramanmaraş suffered extensive damage. Approximately 6650 buildings were destroyed, with many more severely damaged. In Syria, towns such as Aleppo and Idlib, already weakened by war, saw thousands of buildings reduced to rubble.
• Loss of Life: The earthquake resulted in a tragic loss of life. Initial reports estimated that over 50,000 people were killed. The death toll was particularly high in densely populated areas where buildings were not earthquake-resistant.
• Injuries: In Turkey, over 107,000 people were reported injured, while in Syria, thousands more sustained injuries. The exact number in Syria is harder to determine due to the ongoing conflict and less comprehensive reporting.
• Economic Cost: The estimated cost of the 2023 Turkey-Syria earthquake is approximately $84.1 billion. This figure includes significant losses in housing and national income. In Turkey, the direct physical damages alone are estimated at $34.2 billion, with the total cost of recovery and reconstruction expected to be much higher. The estimated total impact in Syria, including physical damages and economic losses, is around $5.2 billion. This disaster has had profound economic implications for both countries, exacerbating existing vulnerabilities and necessitating extensive international aid for recovery efforts.
• Infrastructure Damage: Key infrastructure, including roads, bridges, and utilities, was heavily damaged. This hampered rescue and relief efforts, particularly in remote and conflict-affected areas of Syria.

What were the secondary effects of the Turkey-Syria earthquake?

The secondary effects exacerbated the disaster’s impact:

• Fires: Fires broke out in several locations due to ruptured gas lines and electrical faults caused by the earthquake. These fires further destroyed buildings and claimed lives. One notable instance was the fire in the Iskenderun port, which led to significant damage and disruption in rescue and relief efforts. The fires were exacerbated by ruptured gas lines and electrical faults, posing additional hazards to already vulnerable areas and complicating the immediate response to the disaster.
• Homelessness: Millions of people were rendered homeless, forced to live in makeshift shelters or temporary camps in harsh winter conditions, leading to additional health risks. An estimated 1.5 million people in Turkey and 5.3 million people in Syria were rendered homeless.
• Economic Impact : The economic impact was severe, with businesses destroyed and economic activity disrupted. The cost of rebuilding and the economic losses were estimated to run into billions of dollars.
• Health Crisis: The collapse of hospitals and health centres and the cold weather created a health crisis. Outbreaks of diseases became a concern due to poor sanitary conditions in the makeshift camps. The immediate aftermath saw outbreaks of food and water-borne diseases, including diarrhoea, due to contaminated water and poor sanitary conditions in makeshift camps. Respiratory infections also became prevalent as people were forced to live in crowded and unsanitary conditions. In addition to these, there were rising cases of vaccine-preventable diseases, exacerbated by the interruption in routine vaccination services. In particular, conditions like measles and tetanus posed a higher risk.
• Aftershocks: The region experienced a series of powerful aftershocks, significantly impacting recovery efforts. The most notable aftershock occurred just nine hours later, measuring magnitude 7.5. It further devastated already weakened structures and complicated rescue operations. These aftershocks continued for weeks, with magnitudes reaching 6.7, adding to the destruction and hampering relief efforts. The aftershocks caused additional collapses of damaged buildings, triggered landslides, and led to further hazards such as gas leaks and fires. These ongoing seismic activities not only posed a continuous threat to rescue workers and survivors but also prolonged the psychological and physical stress on the affected communities.

Immediate Responses

The immediate responses to the earthquake were swift but varied in effectiveness:

• Rescue Operations: Local people began to search for survivors in the rubble. Rescue teams from Turkey and international organisations mobilised quickly to search for survivors. Specialised equipment and sniffer dogs were used to locate people trapped under the rubble.
• Local Business Contributions: The Turkish private sector contributed over $11 million in in-kind donations. These donations included essential supplies such as blankets, tents, portable toilets, and mobile kitchens. Turkish businesses also assisted with accommodation, translation services, and transportation for humanitarian aid and rescue efforts.
• Emergency Aid: Emergency aid, including food, water, medical supplies, and blankets, was distributed. The government and NGOs, such as The Red Cross, MSF (Doctors Without Borders), Save the Children, UNICEF, and Islamic Relief Worldwide, set up emergency shelters and field hospitals and supported those affected.
• International Assistance: Numerous countries and international organisations provided aid, including rescue teams, financial assistance, and humanitarian supplies. This was crucial in Syria, where local capacities were overwhelmed. The United Nations launched significant financial appeals to aid the affected regions. The UN issued a $1 billion appeal to assist over five million people in Turkey, covering needs such as food security, protection , education, water, and shelter for three months. A $397 million appeal was launched for Syria to support nearly five million people requiring emergency relief. The UN’s efforts included delivering hot meals, tents, warm clothing, and medical supplies and providing psychosocial support and child-friendly spaces in the affected areas.

Long-term Responses

The long-term responses have focused on rebuilding and rehabilitation:

• Reconstruction: Efforts to rebuild homes, schools, hospitals, and infrastructure are ongoing. In Turkey, there is a focus on constructing earthquake-resistant buildings to prevent future disasters. The World Bank approved $1 billion in financing to support Turkey’s recovery efforts. This funding is directed towards restoring essential public services and rebuilding resilient rural housing in the earthquake-affected areas.
• Economic Recovery: Programs to support economic recovery, including grants and loans for businesses and individuals affected by the earthquake, are being implemented. With funding from Sweden, the United Nations Development Programme (UNDP) provided $4.5 million in grants to small businesses across the 11 worst-affected provinces. This program aimed to revive local economies by supporting small enterprises, with grants ranging from TRY30,000 (approximately $1,150) to TRY300,000 (approximately $11,500). The program also included business advisory services and vocational training to improve entrepreneurial skills.
• Psychological Support: Mental health support services have been established to help survivors cope with trauma and loss.
• Preparedness and Mitigation: Both countries are improving earthquake preparedness and response capabilities. This includes updating building codes, conducting public awareness campaigns, and improving emergency response systems.

Date and Location:

February 6, 2023, near Gaziantep, Turkey, near the Syrian border.

7.8, one of the region’s most devastating recent earthquakes.

Economic Context:

• Turkey : Upper-middle-income country (NEE) with strong industrial and agricultural sectors.
• Syria : Low-income country, severely impacted by civil war.

Tectonic activity along the East Anatolian Fault, a strike-slip fault between the Anatolian and Arabian Plates.

Primary Effects:

• Building Collapse : Thousands of buildings were destroyed in Turkey and Syria.
• Loss of Life : Over 50,000 fatalities.
• Injuries : Over 107,000 injuries in Turkey.
• Infrastructure Damage : Severe damage to roads and utilities.

Secondary Effects:

• Fires : Fires from ruptured gas lines and electrical faults.
• Homelessness : Millions rendered homeless.
• Economic Impact : Economic losses in billions of dollars.
• Aftershocks : Continued aftershocks, including a magnitude 7.5.

Immediate Responses:

• Rescue Operations : Local and international rescue teams mobilised.
• Local Business Contributions : Over $11 million in essential supplies.
• Emergency Aid : Distribution of food, water, and medical supplies.
• International Assistance : Aid from multiple countries and organisations.

Long-term Responses:

• Reconstruction : Efforts supported by $1 billion from the World Bank.
• Economic Recovery : $4.5 million in grants from UNDP for small businesses.
• Psychological Support : Mental health services established.
• Preparedness and Mitigation : Improvements in earthquake preparedness and building codes.

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Turkey Earthquake

Syllabus: Disaster Management/ Geography: Earthquake/ International Relations/ Disaster Relief

Source: IE , Th , DTE , TH

  Direction: This article is in continuation of yesterday’s article on the same issue . Here we will be covering other issues related to Earthquake

Context : South-eastern Turkey, near the Syrian border, was struck by a powerful Earthquake of 7.8 on the Richter Scale.

Why have the buildings collapsed in the “pancake mode” (like a pack of cards)?

• Shallower earthquakes can be more destructive.
• Non-enforcement of safe building construction and non-adherence to seismic building codes: Many of the buildings are already built, and seismic retrofitting may be expensive or not considered a priority compared to other socio-economic challenges of Turkey and Syria

How do Satellites help in Rescue and Recovery efforts during an Earthquake ?

• Satellite imaging enables humanitarian aid to better deliver water and food by mapping the condition of roads, bridges, and buildings, and – most crucially – identifying populations trying to escape potential aftershocks.
• Radar satellites will complement the imaging information, as they also operate at night and through clouds, image landslides and even very small changes in altitude.
• Generating Maps: Images are transformed into impact or change maps for rescue workers, flood alert maps for the public, and mapping of burnt or flooded areas with damage estimates for decision-makers.
• “R econstruction observatories “, have been carried out after major disasters (e.g. Haiti in 2021 and in Beirut after the 2019 port explosion) to monitor reconstruction planning

India’s Proactiveness in Disaster Relief:

• Turkey (2023): India is sending an Army medical team, National Disaster Relief Force (NDRF) personnel, and medical supplies
• Nepal (2015): The NDRF deployed 16 of its urban search and rescue (USAR) teams , which comprised more than 700 rescuers in the country
• Japan (2011): In the aftermath of the 2011 Tsunami, India also sent 46 members of the National Disaster Response Force (NDRF) to search and rescue in the town of Onagawa. It was their first overseas operation
• Sri Lanka (2004, Operation Rainbow): Despite being the victim of the 2004 Tsunami itself, India sent its forces to carry out rescue operations, called “ Operation Rainbow ”, in Sri Lanka hours after the Tsunami struck the country.

“ It is not the disaster, but the lack of preparedness for the disaster that kills ”. Thus, disaster preparedness is one of the most vital components of disaster management.

Related news:

Turkey invoked the International Charter on “Space and Major Disasters ”, just after the Earthquake.

About the International Charter on “Space and Major Disasters ”:

The charter was created by the National Space Research Centre and the European Space Agency in 1999, (now has 17-member space agencies). It aims to provide free satellite imagery as quickly as possible over the disaster area.

Insta Links

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Q. Examine the vulnerability of India to earthquakes and propose short, medium and long-term actions to alleviate the risks associated. (250 words)

  Discuss the factors that cause earthquakes. Why are Earthquakes more common in certain parts of the world than others? Discuss the role of disaster planning in its management. (15M)

Prelims Links:

Turkey is located between

(a) Black Sea and Caspian Sea

(b) Black Sea and Mediterranean Sea

(c) Gulf of Suez and Mediterranean Sea

(d) Gulf of Aqaba and Dead Sea

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