23 October 2011 Van (Turkey) earthquake

An earthquake of Mw7.2 on 23 October 2011 occurred in the Van region of Eastern Turkey. The main shock and long series aftershocks caused significant damage and claimed 644 lives. The particular features and the lessons learned are covered.     

Evaluation of liquefaction in Karasu River floodplain after the October 23, 2011, Van (Turkey) earthquake

Natural Hazards - The eastern shore of Lake Van was shaken by a powerful earthquake (M w 7.2) on October 23, 2011. The epicenter of the earthquake was located at about 30 km north of the...     

Evaluations on the relation of RC building damages with structural parameters after May 19, 2011 Simav (Turkey) earthquake

An earthquake has struck Simav, Kutahya, located in the western part of Turkey on May 19, 2011. This paper focuses on the evaluation of the regional damage data and detailed investigation on a set of selected reinforced concrete buildings in Simav county center. The soil properties in Simav are examined in detail using multi-channel analysis of surface wave measurements, boreholes and laboratory test data. The damages are observed to be independent of soil conditions being hilly or plain, both in regional and Simav county center level. However, a slight relation is observed: as the soil period increases, so does the damage. The most damaged buildings are the four story buildings, resembling the case after some other earthquakes in Turkey. Regarding the detailed numerical evaluations on the building set, the properties highly correlated with seismic damage are investigated. Based on the obtained findings, it is concluded that the global building properties may not be enough to establish a strong relation with damage due to the local damages at the structural member level, especially for smaller seismic events.     

Time-dependent analysis of aftershock events and structural impacts on intraplate crustal seismicity of the Van earthquake (Mw 7.1, 23 October 2011), E-Anatolia

The Van earthquake (M _W 7.1, 23 October 2011) in E-Anatolia is typical representative of intraplate earthquakes. Its thrust focal character and aftershock seismicity pattern indicate the most prominent type of compound earthquakes due to its multifractal dynamic complexity and uneven compressional nature, ever seen all over Turkey. Seismicity pattern of aftershocks appears to be invariably complex in its overall characteristics of aligned clustering events. The population and distribution of the aftershock events clearly exhibit spatial variability, clustering-declustering and intermittency, consistent with multifractal scaling. The sequential growth of events during time scale shows multifractal behavior of seismicity in the focal zone. The results indicate that the extensive heterogeneity and time-dependent strength are considered to generate distinct aftershock events. These factors have structural impacts on intraplate seismicity, suggesting multifractal and unstable nature of the Van event. Multifractal seismicity is controlled by complex evolution of crustal-scale faulting, mechanical heterogeneity and seismic deformation anisotropy. Overall seismicity pattern of aftershocks provides the mechanism for strain softening process to explain the principal thrusting event in the Van earthquake. Strain localization with fault weakening controls the seismic characterization of Van earthquake and contributes to explain the anomalous occurrence of aftershocks and intraplate nature of the Van earthquake.     

Combination of double couple and non-double couple events during the Van,Turkey, 2011 earthquake sequence

A combination of double couple (DC) and non-double couple (non-DC) earthquakes hit Eastern Turkey, in the vicinity of Lake Van, in October–November 2011. Teleseismic waveform inversion was used to find the best fitting double couple and deviatoric moment tensors on four large and medium sized events of this sequence. The aftershocks of the Mw = 7.1, 2011/10/23:10:41 earthquake built a NE–SW aftershock zone where the Mw = 5.7, 2011/10/25 aftershock was located. The Mw = 6.0, 2011/10/23:20:45 event was located around the terminal section of the Mw = 7.1 aftershock zone which might be triggered by this event (aftershocks of this event propagated from W to E to build a W–E aftershock zone where the Mw = 5.7, 2011/11/09 event was located). For these events the calculated best fitting grid search parameters are not very different from GCMT results, but DC components, after deviatoric moment tensor inversion, represent much more difference with GCMT and grid search. The important feature of deviatoric moment tensor inversion is the existence of a notable compensated linear vector dipole (CLVD) component on the Mw = 5.7, 2011/10/25:14:55 and Mw = 5.7, 2011/11/09:19:23 aftershocks. According to the regional seismotectonics, these CLVD components could be related to crustal rheology and volcanic activities. Based on the results, the existence of a cylindrical aftershock distribution could be taken as an indication of induced seismic activity on complex-ring structures resulted from magma or water–magma injection. However, the existence of Karst like structures suggests that the CLVD components may be under the influence of high-pressure water or gas injection rather than magma.     

The van earthquake on October 23, 2011: Natural and technogenic causes

A measurable effect of mass bombing on weak to moderate seismicity, endogenous microseism intensity, and acceleration of tectonic processes has been found. This effect is seen in the regime of strong and catastrophic earthquakes, a decrease in magnitude and time for their preparation, and lesser seismic hazard. The M = 7.8 Van Earthquake on October 23, 2011, was induced to occur early due to mass bombing in Libya and other regions of North Africa; however, the induced character caused its magnitude to be less by several tenths than it might have been.     

Liquefaction-related building damage in Adapazari during the Turkey earthquake of August 17, 1999

The goal of this paper is to present especially the source and the type of liquefaction-related failures of those buildings which satisfied the structural codes of buildings and practices but experienced settlement, tilting and overturning in Adapazari during the Turkey earthquake of August 17, 1999. In this context, the Adapazari region is first evaluated in terms of geological setting, tectonics, seismicity and liquefaction susceptibility based on in situ and laboratory test data. In addition, the number of stories, types of buildings and their related failures have been mapped accordingly. Furthermore, laboratory model tests are conducted to enforce and/or confirm the type of building's failures with particular reference to their geometrical shape and the number of stories assuming that the models representing buildings satisfy the structural codes of buildings and practices.     

Atypical soil hardening during the Tohoku earthquake of March 11, 2011 (Mw = 9.0)

Doklady Earth Sciences - Based on the records of KiK-net vertical arrays, models of soil behavior down to depths of ~100–200 m in the near-fault zones during the Tohoku earthquake are...     

Assessment of liquefaction and lateral spreading on the shore of Lake Sapanca during the Kocaeli (Turkey) earthquake

The 1999 Kocaeli earthquake of Turkey (M_w = 7.4) caused great destruction to buildings, bridges and other facilities, and a death tall of about 20,000. During this earthquake, severe damages due to soil liquefaction and associated ground deformations also occurred widespread in the eastern Marmara Region of Turkey. Soil liquefaction was commonly observed along the shorelines. One of these typical sites is Sapanca town founded on the shore of Lake Sapanca. This study was undertaken as quantitative measurement of ground deformations induced by liquefaction along the southern shore of Lake Sapanca. The permanent lateral ground deformation was measured through the aerial photogrammetry technique at several locations both along the shoreline and in the town. In situ soil profiles and material properties at Sapanca area were obtained based on the data from 55 borings and standard penetration tests (SPT), and laboratory tests, respectively. The data and the empirical methods recommended by an NCEER workshop were employed to evaluate the liquefaction resistance of the soils. In addition, simple shaking tests on a limited number of samples were also performed. The permanent ground displacements were estimated from the existing empirical models, sliding block method and residual visco-elastic finite element methods. Then these estimations were compared with the observed ground displacements. The assessments suggested that liquefaction at Sapanca have occurred within Quaternary alluvial fan deposits at depths 1 and 14 m, and the major regions of liquefaction and associated ground deformations were located along the shore and creeks. The evaluations also indicated that for sites with no sand boils but with ground displacement greater than 1 m, thickness of the non-liquefiable layer was large. It is also noted that no liquefaction-induced ground surface disruption is expected at the site when the thickness of the liquefiable and non-liquefiable layers vary between 0.5 and 1.5 m, and 3.5 and 5.5 m, respectively. Except one model, all the empirical models employed in the study over-predicted the observed lateral ground displacements, while sliding block method and residual visco-elastic finite element methods yielded reasonably good results if the known properties of liquefied soils are used.     

Sedimentary evolution and environmental history of Lake Van (Turkey) over the past 600 000 years

The lithostratigraphic framework of Lake Van, eastern Turkey, has been systematically analysed to document the sedimentary evolution and the environmental history of the lake during the past ca 600 000 years. The lithostratigraphy and chemostratigraphy of a 219 m long drill core from Lake Van serve to separate global climate oscillations from local factors caused by tectonic and volcanic activity. An age model was established based on the climatostratigraphic alignment of chemical and lithological signatures, validated by ⁴⁰Ar/³⁹Ar ages. The drilled sequence consists of ca 76% lacustrine carbonaceous clayey silt, ca 2% fluvial deposits, ca 17% volcaniclastic deposits and 5% gaps. Six lacustrine lithotypes were separated from the fluvial and event deposits, such as volcaniclastics (ca 300 layers) and graded beds (ca 375 layers), and their depositional environments are documented. These lithotypes are: (i) graded beds frequently intercalated with varved clayey silts reflecting rising lake levels during the terminations; (ii) varved clayey silts reflecting strong seasonality and an intralake oxic–anoxic boundary, for example, lake‐level highstands during interglacials/interstadials; (iii) CaCO₃‐rich banded sediments which are representative of a lowering of the oxic–anoxic boundary, for example, lake level decreases during glacial inceptions; (iv) CaCO₃‐poor banded and mottled clayey silts reflecting an oxic–anoxic boundary close to the sediment–water interface, for example, lake‐level lowstands during glacials/stadials; (v) diatomaceous muds were deposited during the early beginning of the lake as a fresh water system; and (vi) fluvial sands and gravels indicating the initial flooding of the lake basin. The recurrence of lithologies (i) to (iv) follows the past five glacial/interglacial cycles. A 20 m thick disturbed unit reflects an interval of major tectonic activity in Lake Van at ca 414 ka bp . Although local environmental processes such as tectonic and volcanic activity influenced sedimentation, the lithostratigraphic pattern and organic matter content clearly reflect past global climate changes, making Lake Van an outstanding terrestrial archive of unprecedented sensitivity for the reconstruction of the regional climate over the last 600 000 years.     

Measures for groundwater security during and after the Hanshin-Awaji earthquake (1995) and the Great East Japan earthquake (2011), Japan

Many big earthquakes have occurred in the tectonic regions of the world, especially in Japan. Earthquakes often cause damage to crucial life services such as water, gas and electricity supply systems and even the sewage system in urban and rural areas. The most severe problem for people affected by earthquakes is access to water for their drinking/cooking and toilet flushing. Securing safe water for daily life in an earthquake emergency requires the establishment of countermeasures, especially in a mega city like Tokyo. This paper described some examples of groundwater use in earthquake emergencies, with reference to reports, books and newspapers published in Japan. The consensus is that groundwater, as a source of water, plays a major role in earthquake emergencies, especially where the accessibility of wells coincides with the emergency need. It is also important to introduce a registration system for citizen-owned and company wells that can form the basis of a cooperative during a disaster; such a registration system was implemented by many Japanese local governments after the Hanshin-Awaji Earthquake in 1995 and the Great East Japan Earthquake in 2011, and is one of the most effective countermeasures for groundwater use in an earthquake emergency. Emphasis is also placed the importance of establishing of a continuous monitoring system of groundwater conditions for both quantity and quality during non-emergency periods.     

Strong ground motion during the largest aftershock (Mw=5.8) of the 1999 Izmit earthquake, Turkey

We present a preliminary study of strong ground motion during the largest aftershock (M_w 5.8) of the 1999 Izmit earthquake (M_w 7.4), Turkey, at 11:55 on 13 September 1999. The peak ground acceleration observed near the epicentre of this aftershock was in agreement with that predicted by standard empirical prediction equations. Its spectral source parameters of the largest aftershock are also typical for a M_w 5.8 earthquake. At greater epicentral distances, there is an order-of-magnitude in scatter in peak ground acceleration values for this aftershock, which is attributed to site effects. The presence of thick layers of low-velocity sediments caused significant amplification of S-waves in the Avcılar district of Istanbul, at frequencies of 1 Hz, explaining the observed concentration of damage there as a result of the Izmit mainshock.     

Strong ground motion estimation in the Sea of Marmara region (Turkey) based on a scenario earthquake

We perform a broadband frequency bedrock strong ground motion simulation in the Marmara Sea region (Turkey), based on several fault rupture scenarios and a source asperity model. The technique combines a deterministic simulation of seismic wave propagation at low frequencies with a semi-stochastic procedure for the high frequencies. To model the high frequencies, we applied a frequency-dependent radiation pattern model, which efficiently removes the effective dependence of the pattern coefficient on the azimuth and take-off angle as the frequency increases. The earthquake scenarios considered consist of the rupture of the closest segments of the North Anatolian Fault System to the city of Istanbul. Our scenario earthquakes involve the rupture of the entire North Anatolian Fault beneath the Sea of Marmara, namely the combined rupture of the Central Marmara Fault and North Boundary Fault segments. We defined three fault rupture scenarios based on the location of the hypocenter, selecting a preferred hypocentral location near a fault bend for each case. We analysed the effect of location of the asperity, within the Central Marmara Fault, on the subsequent ground motion, as well as the influence of anelasticity on the high-frequency attenuation characteristics. The fault and asperity parameters for each scenario were determined from empirical scalings and from results of kinematic and dynamic models of fault rupture. We calculated the resulting time series and spectra for ground motion at Istanbul and evaluated the sensitivity of the predictions to choice of model parameters. The location of the hypocenter is thus shown to be a critical parameter for determining the worst scenario earthquake at Istanbul. We also found that anelasticity has a significant effect on the regional attenuation of peak ground accelerations. Our simulated ground motions result in large values of acceleration response spectra at long periods, which could be critical for building damage at Istanbul during an actual earthquake.     

Liquefaction potential evaluation of the quaternary alluvium, Western Ankara (Turkey)

Liquefaction of the soils is a major problem during and after earthquakes, and can lead to severe damage. A wide range of experience in dealing with natural hazards was gained in the capital city of Ankara after several earthquakes occured in Kaman (1938), Gerede (1944), and Duzce (1999), and in later events. The recent findings after the Orta (2000) and Bala (2005, 2007) earthquakes proved that Ankara should not be designated as a nonseismic hazard zone, as it has been previously. The Quaternary age alluvium is located in the nearby suburbs of Etimesgut, Macunkoy, Cuglu, Avdan, and Kazan. A high density of population and structures is spread over this alluvium, which contains a high percentage of cohesive soils associated with sand and gravel lenses. The depths of the groundwater level ranges between 6.0 and 8.0?m in west Etimesgut, 3.0?m in Macunkoy, 5.0 to 7.0?C8.0?m in Cuglu/Avdan, and 4.5?C7.0?m in southern Kazan. The average S wave velocities of the alluvium derived from the ReMi were 140?m/s in Etimesgut, 200?m/s in Macunkoy, 134?m/s in Cuglu/Avdan, and 200?m/s in Kazan, respectively. Liquefaction evaluation is conducted by standard penetration blow count, shear wave velocity, and threshold acceleration. Varying horizontal accelerations of the input motions in the soil stratigraphy were generated via the Quad4m program. Geotechnical investigation and proper soil improvement should be carried out in order to prevent structural damage.     

An application of regional time and magnitude predictable model for long-term earthquake prediction in the vicinity of October 8, 2005 Kashmir Himalaya earthquake

A regional time and magnitude predictable model has been applied to estimate the recurrence intervals for large earthquakes in the vicinity of 8 October 2005 Kashmir Himalaya earthquake (25°–40°N and 65°–85°E), which includes India, Pakistan, Afghanistan, Hindukush, Pamirs, Mangolia and Tien-Shan. This region has been divided into 17 seismogenic sources on the basis of certain seismotectonics and geomorphological criteria. A complete earthquake catalogue (historical and instrumental) of magnitude Ms ≥ 5.5 during the period 1853–2005 has been used in the analysis. According to this model, the magnitude of preceding earthquake governs the time of occurrence and magnitude of future mainshock in the sequence. The interevent time between successive mainshocks with magnitude equal to or greater than a minimum magnitude threshold were considered and used for long-term earthquake prediction in each of seismogenic sources. The interevent times and magnitudes of mainshocks have been used to determine the following predictive relations: logT _t = 0.05 M _min + 0.09 M _p − 0.01 log M ₀ + 01.14; and M _f = 0.21 M _min − 0.01 M _p + 0.03 log M ₀ + 7.21 where, T _t is the interevent time of successive mainshocks, M _min is minimum magnitude threshold considered, M _p is magnitude of preceding mainshock, M _f is magnitude of following mainshock and M ₀ is the seismic moment released per year in each seismogenic source. It was found that the magnitude of following mainshock (M _f) does not depend on the interevent time (T _t), which indicates the ability to predict the time of occurrence of future mainshock. A negative correlation between magnitude of following mainshock (M _f) and preceding mainshock (M _p) indicates that the larger earthquake is followed by smaller one and vice versa. The above equations have been used for the seismic hazard assessment in the considered region. Based on the model applicability in the studied region and taking into account the occurrence time and magnitude of last mainshock in each seismogenic source, the time-dependent conditional probabilities (PC) for the occurrence of next shallow large mainshocks (Ms ≥ 6.5), during next 20 years as well as the expected magnitudes have been estimated.     

Preliminary analysis of the self-similarity of the aftershocks of the Japanese earthquake on March 11, 2011

The quantitative parameters of the self-similarity of the aftershocks of the Japanese earthquake on March 11, 2011 were obtained. The parameters p in the Omori law (1.06), b in the Gutenberg-Richter law (0.61), and the fractal dimension (D) of the earthquake epicenters (1.52) were determined. Self-similarity is manifested in a range of two orders of temporal and spatial scales and four units of magnitude. The stability in time of parameter p and spatial variations in b and p parameters were revealed.     

Peralkaline felsic magmatism at the Nemrut volcano,Turkey: impact of volcanism on the evolution of Lake Van (Anatolia) IV

Nemrut volcano, adjacent to Lake Van (Turkey), is one of the most important peralkaline silicic centres in the world, where magmatism for ~570,000 years has been dominated by peralkaline trachytes and rhyolites. Using onshore and Lake Van drill site tephra samples, we document the phenocryst and glass matrix compositions, confirming a complete spectrum from very rare mafic to dominantly silicic magmas. Magma mixing has been common and, along with the multi-lineage nature of the magmas, indicates that Nemrut has been a very open system where, nevertheless, compositionally zoned caps developed during periods of relative eruptive quiescence. Geothermometry suggests that the intermediate-silicic magmas evolved in an upper crustal magma reservoir at temperatures between 1100 and 750 °C, at fO₂ close to the FMQ buffer. The silicic magmas either were halogen poor or exsolved a halogen-rich phase prior to or during eruption. An unusual Pb-rich phase, with up to 98.78 wt% PbO, is interpreted as having exsolved from the intermediate-rhyolitic magmas.     

Evaluation of a nonlinear seismic geotechnical site response analysis method subjected to earthquake vibrations (case study: Kerman Province, Iran)

Equivalent static load and dynamic analyses methods are usually used for designing structures under and subjected to earthquake excitations. Estimation of site response from an earthquake is fundamental step to anticipate the possible damages and then to try to mitigate them. In this paper, the effect of nonlinearity on site response analyses summarized and evaluating ground surface response taking into account the local soil and subsurface soils properties for the proposed bridge over the river at Sirdjan Boulevard road subjected to earthquake vibration and provokes with assumption of rigid (viscoelastic) and elastic half space bedrock and quantify the site effect on the surface over a number of geotechnical areas has been notified. First, by field investigation, the required data were collected and by primary processing the acceptable data were selected. Then, in nonlinear analysis, for elastic and rigid half space bedrock, standard hyperbolic model was selected and executed, and then the results were compared to each other. The critical point of this work was to develop and use a computer code by the authors, named the “Abbas Converter”, with several advantages, such as work and quick installation, operating as a connecter function between the used softwares and generating the input data corresponding to defined format for them. Its output results can easily be exported to the other used softwares in this study. This code can make and render this study more easily than the previous softwares have done, and take over the encountered problem. This study clearly showed the applicability of the “Abbas Converter” for evaluation of site response with bedrock-type assumption on soil behavior under the earthquake excitations. The proposed scheme is used to analyze the ground motion data from the Bam earthquake in Kerman Province, Iran (2003, M_w 6.5).