Journal articles: 'Anatolian Fault; Earthquakes'

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Doğangün, Adem, Burak Yön, Onur Onat, Mehmet Emin Öncü, and Serkan Sağıroğlu. "Seismicity of East Anatolian of Turkey and Failures of Infill Walls Induced by Major Earthquakes." Journal of Earthquake and Tsunami 15, no. 04 (March 13, 2021): 2150017. http://dx.doi.org/10.1142/s1793431121500172.

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There are three major fault zones in Turkey scattered around the country known as East Anatolian Fault (EAF), North Anatolian Fault (NAF) and Anatolian-Aegean Subduction Zone (AASZ). Last two decades, EAF has been rather quiescent compared with NAF. However, this quiescence was broken in the beginning of the millennium. The strong shaking was started in 2003 with Bingöl earthquake (Mw = 6.3) and the last earthquake on the EAF is the Sivrice-Elazığ (Mw = 6.8) on January 24, 2020. Strong seismicity of these faults damaged the structures severely and caused death of the habitants. This study aims to present, seismotectonic of the region, general characteristics of the earthquakes and more specifically to report structural damage of infill walls of the structure’s damages caused by these earthquakes. Damage evaluation and identification of the observed infill wall damages due to 2003 Bingöl, 2011 Van earthquakes and January 24, 2020 Sivrice-Elazığ earthquake occurred Turkey’s Eastern region, were presented, and possible solutions were suggested. Moreover, the effects of the infill walls on the behavior of structures under static and dynamic load cases are discussed that experienced in these earthquakes. Damages are classified according to formations such as in-plane or out-of-plane, evaluations and the results obtained from the discussions are presented for each category.

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Acarel, Diğdem, Musavver Didem Cambaz, Fatih Turhan, Ahu Kömeç Mutlu, and Remzi Polat. "Seismotectonics of Malatya Fault, Eastern Turkey." Open Geosciences 11, no. 1 (December 31, 2019): 1098–111. http://dx.doi.org/10.1515/geo-2019-0085.

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Abstract Turkey is located in a seismically active region with a complex tectonic history. In order to perform seismic risk assessment precisely, major fault zones (North Anatolian Fault Zone and East Anatolian Fault Zone) that are well defined are monitored continuously. It is a widely known fact that intraplate settings, such as Anatolian Plate, in which devastating earthquakes may occur, need to be observed densely. In this study, we investigate the seismotectonics of Malatya Fault within the Malatya Ovacık Fault Zone (MOFZ), which is one of the major agents responsible for internal deformation acting on Anatolian Plate. Recent geological and paleoseismological studies underline the necessity of comprehending the seismicity and latency of a major earthquake in this fault zone.We applied traditional techniques to investigate data of such a region. Earthquakes that occured in the vicinity of Malatya Fault between the years 2011 and mid-2019 are employed in a detailed analysis. The results of this study are constrained by the distribution of sensor networks in the region, yet allowing to define an active structure which is not included in the active fault map of Turkey, therefore, making a significant contribution to seismic hazard estimation.

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Ozer, Naside, and Savas Ceylan. "Fractal properties and simulation of micro-seismicity for seismic hazard analysis: a comparison of North Anatolian and San Andreas Fault Zones." Research in Geophysics 2, no. 1 (February 14, 2012): 1. http://dx.doi.org/10.4081/rg.2012.e1.

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We analyzed statistical properties of earthquakes in western Anatolia as well as the North Anatolian Fault Zone (NAFZ) in terms of spatio-temporal variations of fractal dimensions, p- and b-values. During statistically homogeneous periods characterized by closer fractal dimension values, we propose that occurrence of relatively larger shocks (M >= 5.0) is unlikely. Decreases in seismic activity in such intervals result in spatial b-value distributions that are primarily stable. Fractal dimensions decrease with time in proportion to increasing seismicity. Conversely, no spatiotemporal patterns were observed for p-value changes. In order to evaluate failure probabilities and simulate earthquake occurrence in the western NAFZ, we applied a modified version of the renormalization group method. Assuming an increase in small earthquakes is indicative of larger shocks, we apply the mentioned model to micro-seismic (M<= 3.0) activity, and test our results using San Andreas Fault Zone (SAFZ) data. We propose that fractal dimension is a direct indicator of material heterogeneity and strength. Results from a model suggest simulated and observed earthquake occurrences are coherent, and may be used for seismic hazard estimation on creeping strike-slip fault zones.

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Yavaşoğlu, Hasan Hakan, Mehmet Nurullah Alkan, Serdar Bilgi, and Öykü Alkan. "Monitoring aseismic creep trends in the İsmetpaşa and Destek segments throughout the North Anatolian Fault (NAF) with a large-scale GPS network." Geoscientific Instrumentation, Methods and Data Systems 9, no. 1 (February 26, 2020): 25–40. http://dx.doi.org/10.5194/gi-9-25-2020.

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Abstract. The North Anatolian Fault Zone (NAFZ) is an intersection area between the Anatolian and Eurasian plates. The Arabian Plate, which squeezes the Anatolian Plate from the south between the Eurasian Plate and itself, is also responsible for this formation. This tectonic motion causes the Anatolian Plate to move westwards with almost a 20 mm yr−1 velocity, which has caused destructive earthquakes in history. Block boundaries that form the faults are generally locked to the bottom of the seismogenic layer because of the friction between blocks and are responsible for these discharges. However, there are also some unique events observed around the world, which may cause partially or fully free-slipping faults. This phenomenon is called “aseismic creep” and may occur through the entire seismogenic zone or at least to some depths. Additionally, it is a rare event in the world located in two reported segments along the North Anatolian Fault (NAF), which are İsmetpaşa and Destek. In this study, we established GPS networks covering those segments and made three campaigns between 2014 and 2016. Considering the long-term geodetic movements of the blocks (Anatolian and Eurasian plates), surface velocities and fault parameters are calculated. The results of the model indicate that aseismic creep still continues with rates of 13.2±3.3 mm yr−1 at İsmetpaşa and 9.6±3.1 mm yr−1 at Destek. Additionally, aseismic creep behavior is limited to some depths and decays linearly to the bottom of the seismogenic layer at both segments. This study suggests that this aseismic creep behavior will not prevent medium- to large-scale earthquakes in the long term.

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Kutoglu, H. S., H. Akcin, H. Kemaldere, and K. S. Gormus. "Triggered creep rate on the Ismetpasa segment of the North Anatolian Fault." Natural Hazards and Earth System Sciences 8, no. 6 (December 9, 2008): 1369–73. http://dx.doi.org/10.5194/nhess-8-1369-2008.

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Abstract. The Ismetpasa segment of the North Anatolian Fault is one of the rare places in the world where aseismic creep event has been observed. This segment was ruptured during both the 1944, Mw=7.2, Gerede and 1951, Mw=6.9, Kursunlu earthquakes. After these earthquakes, the segment has not experienced a major earthquake anymore. Starting from 1957, many studies using different technologies have been carried out to determine the creep rate of the segment. All these studies until 2002 revealed that the creep movement of the segment slowed down. The new observation campaign of the Ismetpasa geodetic network shows that the Ismetpasa segment has ceased the slowing trend and started to gain speed. This might be interpreted as an increasing earthquake risk for this segment.

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SELİM, H. HALUK, and OKAN TÜYSÜZ. "The Bursa–Gönen Depression, NW Turkey: a complex basin developed on the North Anatolian Fault." Geological Magazine 150, no. 5 (March 6, 2013): 801–21. http://dx.doi.org/10.1017/s0016756812000945.

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AbstractIn this study, we show that the southern branch of the North Anatolian Fault has been active since Late Pliocene time and that evidence of activity is supported by geological and seismological data. The southern branch of the North Anatolian Fault consists of four segments from west to east: Yenice–Gönen, Manyas–Mustafakemalpaşa, Uluabat and Bursa. These faults delimit the Bursa–Gönen Depression, with the Bandırma–Mudanya Uplift to the north and Uludağ–Sularya Uplift to the south. The Bursa–Gönen Depression includes Upper Pliocene to Recent sediments that thicken to the south, suggesting a deposition pattern under active fault control. Study of fault kinematics suggests that the Bursa–Gönen Depression started as a small pull-apart basin during Late Pliocene time, and then evolved to a large depression. The faults delimiting this depression are still active and capable of producing future earthquakes.

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Yuce, G., and D. Ugurluoglu. "Technical NoteEarthquake dates and water level changes in wells in the Eskisehir region, Turkey." Hydrology and Earth System Sciences 7, no. 5 (October 31, 2003): 777–81. http://dx.doi.org/10.5194/hess-7-777-2003.

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Abstract. Although satisfactory results have yet to be obtained in earthquake prediction, one of the most common indicators of an anomalous precursor is a change in groundwater level in existing wells. Further wells should thus be drilled in unconfined aquifers since these are more susceptible to seismic waves. The Eskisehir region lies in the transition zone between the Aegean extensional domain and the compressible northern Anatolian block. Limnigraphs, installed in 19 exploration wells in the Eskisehir region, recorded pre-seismic, co-seismic and post-seismic level changes during the earthquakes of 17 August Izmit (Mw= 7.4) and 12 November Duzce (Mw= 7.2) 1999 that occurred along the North Anatolian Fault Zone. The Izmit and Duzce earthquakes affected groundwater levels, especially in confined aquifers. The aquifer characteristics before and after the earthquakes were unchanged so the aquifer is elastic in its behaviour. Further detailed geo-mechanical investigation of the confined aquifer in the Eskisehir region may improve understanding of earthquake prediction. Keywords: earthquake prediction, Eskisehir, hydrological warning, monitoring groundwater levels

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Civico, R., A. Smedile, D. Pantosti, F. R. Cinti, P. M. De Martini, S. Pucci, Z. Çakır, and S. Şentürk. "New trenching results along the İznik segment of the central strand of the North Anatolian Fault (Turkey): an integration with preexisting data." Mediterranean Geoscience Reviews 3, no. 1 (March 2021): 115–28. http://dx.doi.org/10.1007/s42990-021-00054-9.

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AbstractThis paper provides a new contribution to the construction of the complex and fragmentary mosaic of the Late Holocene earthquakes history of the İznik segment of the central strand of the North Anatolian Fault (CNAF) in Turkey. The CNAF clearly displays lower dextral slip rates with respect to the northern strand however, surface rupturing and large damaging earthquakes (M > 7) occurred in the past, leaving clear signatures in the built and natural environments. The association of these historical events to specific earthquake sources (e.g., Gemlik, İznik, or Geyve fault segments) is still a matter of debate. We excavated two trenches across the İznik fault trace near Mustafali, a village about 10 km WSW of İznik where the morphological fault scarp was visible although modified by agricultural activities. Radiocarbon and TL dating on samples collected from the trenches show that the displaced deposits are very recent and span the past 2 millennia at most. Evidence for four surface faulting events was found in the Mustafali trenches. The integration of these results with historical data and previous paleoseismological data yields an updated Late Holocene history of surface-rupturing earthquakes along the İznik Fault in 1855, 740 (715), 362, and 121 CE. Evidence for the large M7 + historical earthquake dated 1419 CE generally attributed to this fault, was not found at any trench site along the İznik fault nor in the subaqueous record. This unfit between paleoseismological, stratigraphic, and historical data highlights one more time the urge for extensive paleoseismological trenching and offshore campaigns because of the high potential to solve the uncertainties on the seismogenic history (age, earthquake location, extent of the rupture and size) of this portion of NAFZ and especially on the attribution of historical earthquakes to the causative fault.

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Yalcin, A., C. Gokceoglu, and H. Sönmez. "Liquefaction severity map for Aksaray city center (Central Anatolia, Turkey)." Natural Hazards and Earth System Sciences 8, no. 4 (July 7, 2008): 641–49. http://dx.doi.org/10.5194/nhess-8-641-2008.

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Abstract. Turkey having a long history of large earthquakes have been subjected to progressive adjacent earthquakes. Starting in 1939, the North Anatolian Fault Zone (NAFZ) produced a sequence of major earthquakes, of which the Mw 7.4 earthquake that struck western Turkey on 17 August 1999. Following the Erzincan earthquake in 1992, the soil liquefaction has been crucial important in the agenda of Turkey. Soil liquefaction was also observed widely during the Marmara and the Düzce Earthquake in 1999 (Sönmez, 2003). Aksaray city center locates in the central part of Turkey and the Tuzgolu Fault Zone passes through near the city center. The fault zone has been generated to moderate magnitude earthquakes. The geology of the Aksaray province basin contains Quaternary alluvial deposits formed by gravel, sand, silt, and clay layers in different thickness. The Tuzgolu Fault Zone (TFZ) came into being after the sedimetation of alluvial deposits. Thus, the fault is younger from lithological units and it is active. In addition, the ground water level is very shallow, within approximately 3 m from the surface. In this study, the liquefaction potential of the Aksaray province is investigated by recent procedure suggested by Sonmez and Gokceoglu (2005). For this purpose, the liquefaction susceptibility map of the Aksaray city center for liquefaction is presented. In the analysis, the input parameters such as the depth of the upper and lower boundaries of soil layer, SPT-N values, fine content, clay content and the liquid limit were used for all layers within 20 m from the surface. As a result, the category of very high susceptibility liquefaction class was not observed for the earthquake scenario of Ms=5.2, 4.9% of the study area has high liquefaction susceptibility. The percentage of the moderately, low, and very low liquefied areas are 28.2%, 30.2%, and 36.3%, respectively. The rank of non-liquefied susceptibility area is less than 1%.

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Houseman, Gregory A. "Why Earthquakes Threaten Two Major European Cities: Istanbul and Bucharest." European Review 26, no. 1 (November 20, 2017): 30–49. http://dx.doi.org/10.1017/s1062798717000448.

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Istanbul and Bucharest are major European cities that face a continuing threat of large earthquakes. The geological contexts for these two case studies enable us to understand the nature of the threat and to predict more precisely the consequences of future earthquakes, although we remain unable to predict the time of those events with any precision better than multi-decadal. These two cities face contrasting threats: Istanbul is located on a major geological boundary, the North Anatolian Fault, which separates a westward moving Anatolia from the stable European landmass. Bucharest is located within the stable European continent, but large-scale mass movements in the upper mantle beneath the lithosphere cause relatively frequent large earthquakes that represent a serious threat to the city and surrounding regions.

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Kutoglu, H. S., R. N. Celik, M. T. Ozludemir, and C. Güney. "New findings on the effects of the İzmit Mw=7.4 and Düzce Mw=7.2 earthquakes." Natural Hazards and Earth System Sciences 11, no. 2 (February 2, 2011): 267–72. http://dx.doi.org/10.5194/nhess-11-267-2011.

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Abstract. The 17 August 1999 İzmit Mw=7.4 and the 12 November 1999 Düzce Mw=7.2 earthquakes caused a 150 km long surface rupture in the western part of the North Anatolian Fault. The coseismic slips along the fault line and the trace of the surface ruptures were studied in detail in Barka (1999), Reilinger et al. (2000), Cakir et al. (2003a, b) and Ergintav (2009) after the earthquakes. However, the basin to the east of Sapanca Lake was a black hole for all investigations because there was no geodetic network and no significant deformation that could be obtained by using InSAR techniques. In this study, findings on the abovementioned basin have been reinterpreted through a GPS network newly explored. This interpretation shows coseismic slips of between 2–3 m, and links the surface rupture to the main branch of the North Anatolian Fault (NAF) in the east Sapanca basin.

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Yavasoglu, Hakan. "Strain Rate Analysis on the Çankiri-Bingöl Segment of the North Anatolian Fault in Turkey." Earth Sciences Research Journal 19, no. 2 (December 17, 2015): 121–27. http://dx.doi.org/10.15446/esrj.v19n2.49063.

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The North Anatolian Fault Zone (NAFZ) is one of the most important fault zones of Turkey and the world. It has produced several high magnitude earthquakes that have resulted in massive loss of lives and resources. National and international research on the North Anatolian Fault zone that Turkey resides on have been realized to better understand and predict the earthquakes produced by it. This study focuses on the Çankırı – Bingöl segment of the NAFZ. The aim of this study is to calculate the strain and latent earthquake potential of the studied area. For this purpose, geodetic data coming from several individual projects have been merged. Strain values have been calculated from the combined data and regions on the fault zone, and strain accumulations have been presented graphically. After calculation, Çankırı, Amasya and Kelkit regions were analyzed. The compressional and extensional deformation has been shown in north and south part of Çankırı basin, respectively. Eastern adjacent area of the Çankırı basin, Amasya region, has the primary branch of the NAF and its subbranches. In the Amasya region, the deformation is mostly on the main branch and the earthquake potential has risen to it. The Kelkit Valley has complex structures and inhomogeneous dispersion. Southeastern and Northwestern part of the Kelkit Valley has varied deformation in micro scale. Consequently, the study results indicate that strain accumulation is concentrated on areas such as the Çankırı basin, Amasya region, and various areas in the Kelkit Valley from west to east. Análisis de la Velocidad de Deformación en el Segmento Çankırı-Bingöl de la Falla de Anatolia del Norte, Turquía. Resumen La Zona de la Falla de Anatolia del Norte (NAFZ, del inglés North Anatolian Fault Zone) es una de las zonas de fallas más importantes de Turquía y del mundo. Esta falla ha generado varios terremotos de gran magnitud que han resultado en pérdidas humanas y de recursos. La investigación nacional e internacional de la Zona de la Falla de Anatolia del Norte, que atraviesa Turquía, se ha realizado con el fin de un mejor entendimiento y predicción de los terremotos que allí se originan. Este análisis se enfoca en el segmento Çankırı-Bingöl de la NAFZ. El objetivo es calcular la tensión y el potencial de terremoto del área de estudio. Con este propósito se recopiló la información geodésica de varios proyectos individuales. Los valores de tensión se calcularon de la información combinada de las regiones que componen la zona de falla y se presentan gráficamente las acumulaciones de tensión. Tras el cálculo de estos valores se analizaron las regiones Çankırı, Amasya y Kelkit. La deformación de compresión y la de extensión aparecen al norte y al sur de la cuenca Çankırı, respectivamente. El área ubicada al Este de la cuenca Çankırı, la región de Amasya, posee la rama principal de la NAFZ y sus subdivisiones. En la región de Amasya la deformación se presenta en la rama principal de la NAFZ, donde se eleva el potencial de movimientos sísmicos. El valle de Kelkit tiene estructuras complejas y dispersión no homogénea. El sudeste y el noroeste del valle Kelkit muestran una deformación variada a microescala. Los resultados de este estudio indican que la acumulación de tensión se concentra en la cuenca Çankırı, la región Amasya y varias áreas del valle Kelkit desde el oeste hacia el este.

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Yalçın, H., A. Kürçer, M. Utkucu, and L. Gülen. "SEISMOTECTONICS OF THE SOUTHERN MARMARA REGION, NW TURKEY." Bulletin of the Geological Society of Greece 50, no. 1 (July 27, 2017): 173. http://dx.doi.org/10.12681/bgsg.11717.

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The Southern Marmara Region is an active deformation area, which is a transition zone between the strike-slip tectonics manifested by the North Anatolian Fault System and the N-S extensional regime of the Aegean Region. We have reviewed tectonic and geological structure of the region, based onseismological studies. We have obtained a total of 37 earthquake moment tensor solutions between 1953 and 2015. In addition, stress tensor analysis has been carried out using 37 earthquake moment tensor solutions. Also long term seismicity were investigated and a,b, Mc values were calculated and mapped. Moment tensor solutions indicate that the source of these earthquakes are mostly NE-trending dextral strike-slip faults and some of them are E-W trending dip-slip normal faults. The stress tensor analysis shows that the direction of the regional compressive stress is NW-SE. The temporal and spatial distrubution of the large earthquakes (1944, 1953, 1964) indicate that the ruptures unilaterally propagate from SW to NE. The 1855 earthquake had been occurred to the east of Manyas Lake. The elapsed time (160 year) and regional stress transfer suggest that the segments to the east of Manyas Lake form a probable seismic gap and this area has a high earthquake risk.

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Öncel, A. O., Ö. Alptekin, and I. Main. "Temporal variations of the fractal properties of seismicity in the western part of the north Anatolian fault zone: possible artifacts due to improvements in station coverage." Nonlinear Processes in Geophysics 2, no. 3/4 (December 31, 1995): 147–57. http://dx.doi.org/10.5194/npg-2-147-1995.

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Abstract. Seismically-active fault zones are complex natural systems exhibiting scale-invariant or fractal correlation between earthquakes in space and time, and a power-law scaling of fault length or earthquake source dimension consistent with the exponent b of the Gutenberg-Richter frequency-magnitude relation. The fractal dimension of seismicity is a measure of the degree of both the heterogeneity of the process (whether fixed or self-generated) and the clustering of seismic activity. Temporal variations of the b-value and the two-point fractal (correlation) dimension Dc have been related to the preparation process for natural earthquakes and rock fracture in the laboratory These statistical scaling properties of seismicity may therefore have the potential at least to be sensitive short- term predictors of major earthquakes. The North Anatolian Fault Zone (NAFZ) is a seismicallyactive dextral strike slip fault zone which forms the northern boundary of the westward moving Anatolian plate. It is splayed into three branches at about 31oE and continues westward toward the northern Aegean sea. In this study, we investigate the temporal variation of Dc and the Gutenberg-Richter b-value for seismicity in the western part of the NAFZ (including the northern Aegean sea) for earthquakes of Ms > 4.5 occurring in the period between 1900 and 1992. b ranges from 0.6-1.6 and Dc from 0.6 to 1.4. The b-value is found to be weakly negatively correlated with Dc (r=-0.56). However the (log of) event rate N is positively correlated with b, with a similar degree of statistical significance (r=0.42), and negatively correlated with Dc (r=-0.48). Since N increases dramatically with improved station coverage since 1970, the observed negative correlation between b and Dc is therefore more likely to be due to this effect than any underlying physical process in this case. We present this as an example of how man-made artefacts of recording can have similar statistical effects to underlying processes.

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Xu, Jiao, Chengli Liu, and Xiong Xiong. "Source Process of the 24 January 2020 Mw 6.7 East Anatolian Fault Zone, Turkey, Earthquake." Seismological Research Letters 91, no. 6 (September 9, 2020): 3120–28. http://dx.doi.org/10.1785/0220200124.

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Abstract The 24 January 2020 Mw 6.7 earthquake in eastern Turkey was due to the reactivation of the strike-slip faulting between the Arabian and Anatolian plates. To gain insight into the source regime and its relationship with historical earthquakes, we determined the coseismic slip distribution of this event by joint analyses of Interferometric Synthetic Aperture Radar and teleseismic observations. Inversion results indicate that the main rupture asperity occurred in the southwest of the epicenter with a maximum slip of ∼1.9 m, showing a bilateral source process with an average rupture velocity of ∼1.6 km/s, and small slip extended to the surface near the epicenter. The estimated seismic moment is 1.4×1019 N·m, associated with a ∼50 km long and ∼15 km wide fault plane. The aftershocks distribution is obviously complementary with the coseismic rupture zone. That is, the majority of aftershocks clustered in the transitional regions from the large to small slip areas. The 2020 earthquake only ruptured part of the locked zone and could increase the seismic activity in the East Anatolian fault zone during the interseismic phase. Two verified seismic gaps remain unbroken and hazardous.

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Barut, R. Alac, J. Trinder, and C. Rizos. "ANALYSING POST-SEISMIC DEFORMATION OF IZMIT EARTHQUAKE WITH INSAR, GNSS AND COULOMB STRESS MODELLING." ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLI-B1 (June 3, 2016): 417–21. http://dx.doi.org/10.5194/isprsarchives-xli-b1-417-2016.

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On August 17th 1999, a Mw 7.4 earthquake struck the city of Izmit in the north-west of Turkey. This event was one of the most devastating earthquakes of the twentieth century. The epicentre of the Izmit earthquake was on the North Anatolian Fault (NAF) which is one of the most active right-lateral strike-slip faults on earth. However, this earthquake offers an opportunity to study how strain is accommodated in an inter-segment region of a large strike slip fault. In order to determine the Izmit earthquake post-seismic effects, the authors modelled Coulomb stress changes of the aftershocks, as well as using the deformation measurement techniques of Interferometric Synthetic Aperture Radar (InSAR) and Global Navigation Satellite System (GNSS). The authors have shown that InSAR and GNSS observations over a time period of three months after the earthquake combined with Coulomb Stress Change Modelling can explain the fault zone expansion, as well as the deformation of the northern region of the NAF. It was also found that there is a strong agreement between the InSAR and GNSS results for the post-seismic phases of investigation, with differences less than 2mm, and the standard deviation of the differences is less than 1mm.

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Barut, R. Alac, J. Trinder, and C. Rizos. "ANALYSING POST-SEISMIC DEFORMATION OF IZMIT EARTHQUAKE WITH INSAR, GNSS AND COULOMB STRESS MODELLING." ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLI-B1 (June 3, 2016): 417–21. http://dx.doi.org/10.5194/isprs-archives-xli-b1-417-2016.

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On August 17th 1999, a Mw 7.4 earthquake struck the city of Izmit in the north-west of Turkey. This event was one of the most devastating earthquakes of the twentieth century. The epicentre of the Izmit earthquake was on the North Anatolian Fault (NAF) which is one of the most active right-lateral strike-slip faults on earth. However, this earthquake offers an opportunity to study how strain is accommodated in an inter-segment region of a large strike slip fault. In order to determine the Izmit earthquake post-seismic effects, the authors modelled Coulomb stress changes of the aftershocks, as well as using the deformation measurement techniques of Interferometric Synthetic Aperture Radar (InSAR) and Global Navigation Satellite System (GNSS). The authors have shown that InSAR and GNSS observations over a time period of three months after the earthquake combined with Coulomb Stress Change Modelling can explain the fault zone expansion, as well as the deformation of the northern region of the NAF. It was also found that there is a strong agreement between the InSAR and GNSS results for the post-seismic phases of investigation, with differences less than 2mm, and the standard deviation of the differences is less than 1mm.

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Abdikan, S., M. Imamoglu, T. Alasag, M. Toker, S. H. Kutoglu, and S. Sahin. "INSAR ANALYSIS OF AYVACIK 2017 (MW 5.3) EARTHQUAKE SWARM (CANAKKALE, NW-TURKEY)." ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLII-2/W13 (June 5, 2019): 1907–11. http://dx.doi.org/10.5194/isprs-archives-xlii-2-w13-1907-2019.

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Abstract. In this study, the deformation of Ayvacik Canakkale earthquake and aftershocks of 5.3 (Mw), which were observed on 6 February 2017 in Gulpinar Ayvacik and felt from the surrounding cities, were analyzed by InSAR and strain reduction technique. The earthquake is occurred at the Biga peninsula which is located at the south segment of North Anatolian Fault zone. The first shock (Ml&thinsp;=&thinsp;4.8) started on 14 January 2017 in the region, and after the second shock (Ml&thinsp;=&thinsp;5.4) on February 6, 2017, seismic storm continued with the large and small earthquakes. It was seen that 31 of these earthquakes have a size of 4 and above and occurred on the Tuzla fault. Since classical geodetic methods are not performed regularly and frequently, and are spatially provide point-based displacements, they are often insufficient to monitor sudden earthquakes. For this purpose, the deformation values were obtained along the line of sight (LOS) direction of Synesthetic Aperture Radar (SAR) sensor using Differential Interferometric SAR (DInSAR) method. For the geophysical analysis coulomb technique was applied and the continuity of the changes in the sea is determined.

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Briole, Pierre, Athanassios Ganas, Panagiotis Elias, and Dimitar Dimitrov. "The GPS velocity field of the Aegean. New observations, contribution of the earthquakes, crustal blocks model." Geophysical Journal International 226, no. 1 (March 10, 2021): 468–92. http://dx.doi.org/10.1093/gji/ggab089.

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SUMMARY We calculate and analyse the coordinate time-series of 282 permanent GPS stations located in Greece and 47 in surrounding countries. The studied period is 2000–2020. The average GPS time-series length is 6.5 yr. The formal velocity uncertainties are rescaled to be consistent with the velocity scatters measured at 110 pairs of stations separated by less 15 km. We remove the effect of the crustal earthquakes of Mw ≥ 5.3. We quantify and model the post-seismic deformations. Two relaxation times are usually needed: one short of some weeks and one long of 1 yr or more. For the large Mw = 6.9 events of Samothraki 2014 and Methoni 2008, the post-seismic deformation equals or exceeds the coseismic one. We detect at three stations a deformation transient in May 2018 that may correspond to a slow earthquake beneath Zakynthos and northwest Peloponnese, with equivalent magnitude 5.8. The density and accuracy of the velocities make it possible to better quantify several characteristics of the deformation in the Aegean, in particular: (i) the transition from the Anatolian domain, located in the southeast, to the European domain through the western end of the North Anatolian fault; (ii) the north–south extension in the western Aegean; (iii) the east–west extension of the western Peloponnese; (iv) the clockwise rotation of the Pindos; (v) the north–south extension in central Macedonia. Large parts of the central Aegean, eastern Peloponnese and western Crete form a wide stable domain with internal deformation below 2 nstrain yr−1. We build a kinematic model comprising 10 crustal blocks corresponding to areas where the velocities present homogeneous gradients. The blocks boundaries are set to fit with known localized deformation zones, for example, the rift of Corinth, the North Anatolian fault and the Katouna fault. When the velocity steps are clear but not localized, for example, through the Peloponnese, the boundary line is arbitrary and represents the transition zone. The model fits the velocities with a root-mean-square deviation of ±0.9 mm yr−1. At the boundaries between blocks we compare the predicted and observed deformations. We find shear rates of 7.4 and 9.0 mm yr−1 along the Movri and Katouna faults, 14.9 and 8.7 mm yr−1 along the North Anatolian fault near Lemnos and near Skopelos respectively, extension of 7.6, 1.5 and 12.6 mm yr−1 across the Gulf of Patras, the Trichonis Lake and the Ambracian Gulf. The compression across western Epirus is 3.7 mm yr−1. There is a dextral transtensional movement of 4.5 mm yr−1 between the Amorgos and Astypalea islands. Only the Ionian Islands region shows evidence of coupling along the subduction interface.

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Homan, Jacqueline, and Warren J. Eastwood. "The 17 August 1999 Kocaeli (İzmit) Earthquake: Historical Records and Seismic Culture." Earthquake Spectra 17, no. 4 (November 2001): 617–34. http://dx.doi.org/10.1193/1.1423654.

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The 17 August 1999 İzmit, Turkey, earthquake (M∼7.4) was the latest in a long series of large seismic events to occur along the North Anatolian Fault Zone. The detailed recording of earthquakes in the İzmit region, from anti-quity to recent times, has allowed a unique archive to be developed that is invaluable to present day seismologists. Additionally, historical building practices, in particular the incorporation of the hatıl or ringbeam, indicate that adaptations to earthquakes in the form of seismic cultures were present in Turkey during Byzantine and Ottoman times and can be re-evaluated in relation to contemporary building practices. This is particularly important with respect to the potential threat now facing the population of İstanbul, a large proportion of which are in a highly vulnerable position. This paper suggests that “experts” use this seismic knowledge to produce a meaningful account of earthquake hazard for local people in order to reduce marginalization in case of a future event.

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Kutoglu, H. S., H. Akcin, O. Gundogdu, K. S. Gormus, and E. Koksal. "Relaxation on the Ismetpasa segment of the North Anatolian Fault after the Golcuk Mw = 7.4 and Duzce Mw = 7.2 shocks." Natural Hazards and Earth System Sciences 10, no. 12 (December 21, 2010): 2653–57. http://dx.doi.org/10.5194/nhess-10-2653-2010.

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Abstract. The Ismetpasa segment of the North Anatolian Fault (NAF) is a rare place where aseismic fault slip (creep) has been observed. Its creep behaviour has been monitored using different observation methods since the 1950s. The findings obtained from the studies until 1990s showed that the creep rate exponentially decreased before the major shocks in 1999, Golcuk (Mw = 7.4) and Duzce (Mw = 7.2). After these shocks, three GPS periods observation in 2002, 2007 and 2008 were carried out on the geodetic network established around the segment. The evaluations of these observations showed that the creep behaviour relaxed after the major earthquakes. This result demonstrates that the creep behaviour of the Ismetpasa segment might be a warning before future major earthquakes.

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Bouchon, Michel, Hayrullah Karabulut, Mustafa Aktar, Serdar Özalaybey, Jean Schmittbuhl, Marie-Paule Bouin, and David Marsan. "The nucleation of the Izmit and Düzce earthquakes: some mechanical logic on where and how ruptures began." Geophysical Journal International 225, no. 3 (January 29, 2021): 1510–17. http://dx.doi.org/10.1093/gji/ggab040.

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SUMMARY In spite of growing evidence that many earthquakes are preceded by increased seismic activity, the nature of this activity is still poorly understood. Is it the result of a mostly random process related to the natural tendency of seismic events to cluster in time and space, in which case there is little hope to ever predict earthquakes? Or is it the sign that a physical process that will lead to the impending rupture has begun, in which case we should attempt to identify this process. With this aim we take a further look at the nucleation of two of the best recorded and documented strike-slip earthquakes to date, the 1999 Izmit and Düzce earthquakes which ruptured the North Anatolian Fault over ∼200 km. We show the existence of a remarkable mechanical logic linking together nucleation characteristics, stress loading, fault geometry and rupture speed. In both earthquakes the observations point to slow aseismic slip occurring near the ductile-to-brittle transition zone as the motor of their nucleation.

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Yön, Burak, Onur Onat, Mehmet Emin Öncü, and Abdulhalim Karaşi̇n. "Failures of masonry dwelling triggered by East Anatolian Fault earthquakes in Turkey." Soil Dynamics and Earthquake Engineering 133 (June 2020): 106126. http://dx.doi.org/10.1016/j.soildyn.2020.106126.

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Lorenzo-Martín, Francisco, Frank Roth, and Rongjiang Wang. "Elastic and inelastic triggering of earthquakes in the North Anatolian Fault zone." Tectonophysics 424, no. 3-4 (October 2006): 271–89. http://dx.doi.org/10.1016/j.tecto.2006.03.046.

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25

Taymaz, Tuncay, Haluk Eyidog̃an, and James Jackson. "Source parameters of large earthquakes in the East Anatolian Fault Zone (Turkey)." Geophysical Journal International 106, no. 3 (September 1991): 537–50. http://dx.doi.org/10.1111/j.1365-246x.1991.tb06328.x.

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Zabcı, Cengiz. "Spatio-temporal behaviour of continental transform faults: implications from the late Quaternary slip history of the North Anatolian Fault, Turkey." Canadian Journal of Earth Sciences 56, no. 11 (November 2019): 1218–38. http://dx.doi.org/10.1139/cjes-2018-0308.

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The slip history of the North Anatolian Fault (NAF) is constrained by displacement and age data for the last 550 ka. First, I classified all available geological estimates as members of three groups: Model I for the eastern, Model II for the central, and Model III for the western segments where the North Anatolian Shear Zone gradually widens from east to west. The short-term uniform slip solutions yield similar results, 17.5 +4/–3.5 mm/a, 18.9 +3.7/–3.3 mm/a, and 16.9 +1.2/–1.1 mm/a from east to the west. Although these model rates do not show any significant spatial variations among themselves, the correlation with geodetic estimates, ranging between 15 mm/a and 28 mm/a for different sections of the NAF, displays significant discrepancies especially for the central and western segments of the fault. Discrepancies suggest that most strain is accumulated along the NAF, but some portion of it is distributed along secondary structures of the North Anatolian Shear Zone. The deformation rate is constant at least for the last 195 ka, whereas the limited number of data show strain transfer from northern to the southern strand between 195 and 320 ka BP in the Marmara Region when the incremental slip rate decreases to 13.2 +3.1/–2.9 mm/a for the northern strand of the NAF. Considering the possible uncertainties of incremental displacements and their timings, more studies on slip rate are needed at different sites, including major structural elements of the North Anatolian Shear Zone. Although most of the strain is localized along the main displacement zone, the NAF, secondary structures are still capable of generating earthquakes that can hardly reach Mw 7.

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27

Rondoyanni, Th, Ch Georgiou, D. Galanakis, and M. Kourouzidis. "EVIDENCES OF ACTIVE FAULTING IN THRACE REGION (NORTHEASTERN GREECE)." Bulletin of the Geological Society of Greece 36, no. 4 (January 1, 2004): 1671. http://dx.doi.org/10.12681/bgsg.16572.

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Active oblique to strike-slip faults were identified in southern Thrace (northeastern Greece), on the basis of field observations, geological mapping, analysis of geometrical and dynamic characteristics of recent tectonic structures as well as evaluation of their seismic potential. The seismic activity refers mainly to strong earthquakes occurring under the sea, while a minor number of seismic epicenters have been registered on land. According to the historic and recent data, most seismic destructions in this region are due to the influence of the North Anatolian Fault and North Aegean Trough system. The diachronic activity of several faults and the changes in the movement type from clearly normal to oblique-normal or strike-slip, have left clear signs on the existing polished fault planes. Among the numerous faults determined in Thrace, some of them can be characterized as active, according to their geological and morphotectonic characteristics. Taking in to account the faults length, the specific seismotectonic conditions prevailing over the Hellenic territory and the existed empirical relationships, the maximum displacement in case of seismic reactivation was estimated.

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Benjelloun, Yacine, Julia de Sigoyer, Hélène Dessales, Laurent Baillet, Philippe Guéguen, and Mustafa Sahin. "Historical Earthquake Scenarios for the Middle Strand of the North Anatolian Fault Deduced from Archeo-Damage Inventory and Building Deformation Modeling." Seismological Research Letters 92, no. 1 (November 18, 2020): 583–98. http://dx.doi.org/10.1785/0220200278.

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Abstract The city of İznik (ancient Nicaea), located on the middle strand of the North Anatolian fault zone (MNAF), presents outstanding archeological monuments preserved from the Roman and Ottoman periods (first to fifteenth centuries A.D.), bearing deformations that can be linked to past seismic shaking. To constrain the date and intensity of these historical earthquakes, a systematic survey of earthquake archeological effects (EAEs) is carried out on the city’s damaged buildings. Each of the 235 EAEs found is given a quality ranking, and the corresponding damage is classified according to the European Macroseismic Scale 1998 (EMS-98). We show that the walls oriented north–south were preferentially damaged, and that most deformations are perpendicular to the walls’ axes. The date of postseismic repairs is constrained with available archeological data and new C14 dating of mortar charcoals. Three damage episodes are evidenced: (1) between the sixth and late eighth centuries, (2) between the nineth and late eleventh centuries A.D., and (3) after the late fourteenth century A.D. The repartition of damage as a function of building vulnerability points toward a global intensity VIII on the EMS-98. The 3D modeling of a deformed Roman obelisk shows that only earthquakes rupturing the MNAF can account for this deformation. Their magnitude can be bracketed between Mw 6 and 7. Our archeoseismological study complements the historical seismicity catalog and confirms paleoseismological data, suggesting several destructive earthquakes along the MNAF, since the first century A.D. We suggest the fault might still have accumulated enough stress to generate an Mw 7+ rupture.

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Yamamoto, Yojiro, Dogan Kalafat, Ali Pinar, Narumi Takahashi, Remzi Polat, Yoshiyuki Kaneda, and Haluk Ozener. "Seismic velocity structure along the North Anatolian Fault beneath the Central Marmara Sea and its implication for seismogenesis." Geophysical Journal International 228, no. 1 (August 6, 2021): 396–411. http://dx.doi.org/10.1093/gji/ggab351.

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SUMMARY The offshore part of the North Anatolian Fault (NAF) beneath the Marmara Sea is a well-known seismic gap for future M > 7 earthquakes in the sense that more than 250 yr have passed since the last major earthquake in the Central Marmara region. Although many studies discussed the seismic potential for the future large earthquake in this region on the basis of historical record, geodetic and geological observations, it is difficult to evaluate the actual situation on the seismic activity and structure along the NAF beneath the Marmara Sea due to the lack of ocean bottom seismic observations. Using ocean bottom seismometer observations, an assessment of the location of possible asperities that could host an expected large earthquake is undertaken based on heterogeneities in the microseismicity distribution and seismic velocity structure. Specifically, seismic tomography and precise hypocentre estimations are conducted using offshore seismic data whose recording period is 11 months. About five times more microearthquakes are detected with respect to events recorded in a land-based catalogue. A comparison with previously published results from offshore observation data suggests that the seismicity pattern had not changed from 2014 September to 2017 May. The location accuracy of microearthquakes is greatly improved from only the land-based earthquake catalogue, particularly for depth direction. There are several aseismic and inactive zones of microearthquake, and the largest one is detected using land-based seismic observation, whereas other zones are newly detected via offshore observations. The obtained velocity model shows a strong lateral contrast, with two changing points. The western changing point corresponds to a segmentation boundary, where the dip angle of the NAF segments changed. High-velocity zones from tomographic images are characterized by low seismicity eastward of the segment boundary. To the east of 28.50°E, the high-velocity zone becomes thicker in the depth direction and is characterized by low seismicity. Although the low seismic activity alone could be interpreted as both strong coupling and fully creeping, the high-velocity features at the same can be concluded that these zones are consist of brittle material and strong coupling. From comparison with other geodetic and seismic studies, we interpret these zones as locked zones that had been ruptured by the past large earthquakes and could be ruptured by future ones. These zones might accumulate strain since the main shock rupture associated with the 1766 May Ms 7.3 earthquake, the latest major earthquake in this region.

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Boës, X., S. B. Moran, J. King, M. N. Cağatay, and A. Hubert-Ferrari. "Records of large earthquakes in lake sediments along the North Anatolian Fault, Turkey." Journal of Paleolimnology 43, no. 4 (September 17, 2009): 901–20. http://dx.doi.org/10.1007/s10933-009-9376-x.

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31

Karabulut, Hayrullah, Sezim Ezgi Güvercin, Figen Eskiköy, Ali Özgun Konca, and Semih Ergintav. "The moderate size 2019 September Mw 5.8 Silivri earthquake unveils the complexity of the Main Marmara Fault shear zone." Geophysical Journal International 224, no. 1 (September 29, 2020): 377–88. http://dx.doi.org/10.1093/gji/ggaa469.

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SUMMARY The unbroken section of the North Anatolian Fault beneath the Sea of Marmara is a major source of seismic hazard for the city of İstanbul. The northern and currently the most active branch, the Main Marmara Fault (MMF), is segmented within a shear zone and exhibits both partially creeping and locked behaviour along its 150 km length. In 2019 September, a seismic activity initiated near MMF, off-coast the town of Silivri, generating 14 earthquakes ≥ Mw 3.5 in a week. The Mw 5.8 Silivri earthquake, is the largest in the Marmara Sea since the 1963 Mw 6.3 Çınarcık earthquake. Our analyses reveal that the activity started in a narrow zone (∼100 m) and spread to ∼7 km following an Mw 4.7 foreshock within ∼2 d. The distribution of relocated aftershocks and the focal mechanisms computed from regional waveforms reveal that the Mw 5.8 earthquake did not occur on the MMF, but it ruptured ∼60° north-dipping oblique strike-slip fault with significant thrust component located on the north of the MMF. Finite-fault slip model of the main shock shows 8 km long rupture with directivity toward east, where the ruptured fault merges to the MMF. The narrow depth range of the slip distribution (10–13 km) and the aftershock zone imply that the causative fault is below the deep sedimentary cover of the Marmara Basin. The distribution of aftershocks of the Mw 5.8 event is consistent with Coulomb stress increase. The stress changes along MMF include zones of both stress decrease due to clamping and right-lateral slip, and stress increase due to loading.

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32

Palyvos, N., D. Pantosti, C. Zabci, and G. D'Addezio. "Paleoseismological Evidence of Recent Earthquakes on the 1967 Mudurnu Valley Earthquake Segment of the North Anatolian Fault Zone." Bulletin of the Seismological Society of America 97, no. 5 (October 1, 2007): 1646–61. http://dx.doi.org/10.1785/0120060049.

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33

Uchida, N., D. Kalafat, A. Pinar, and Y. Yamamoto. "Repeating earthquakes and interplate coupling along the western part of the North Anatolian Fault." Tectonophysics 769 (October 2019): 228185. http://dx.doi.org/10.1016/j.tecto.2019.228185.

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34

Gülerce, Zeynep, Kadir Buğra Soyman, Barış Güner, and Nuretdin Kaymakci. "Planar seismic source characterization models developed for probabilistic seismic hazard assessment of Istanbul." Natural Hazards and Earth System Sciences 17, no. 12 (December 22, 2017): 2365–81. http://dx.doi.org/10.5194/nhess-17-2365-2017.

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Abstract. This contribution provides an updated planar seismic source characterization (SSC) model to be used in the probabilistic seismic hazard assessment (PSHA) for Istanbul. It defines planar rupture systems for the four main segments of the North Anatolian fault zone (NAFZ) that are critical for the PSHA of Istanbul: segments covering the rupture zones of the 1999 Kocaeli and Düzce earthquakes, central Marmara, and Ganos/Saros segments. In each rupture system, the source geometry is defined in terms of fault length, fault width, fault plane attitude, and segmentation points. Activity rates and the magnitude recurrence models for each rupture system are established by considering geological and geodetic constraints and are tested based on the observed seismicity that is associated with the rupture system. Uncertainty in the SSC model parameters (e.g., b value, maximum magnitude, slip rate, weights of the rupture scenarios) is considered, whereas the uncertainty in the fault geometry is not included in the logic tree. To acknowledge the effect of earthquakes that are not associated with the defined rupture systems on the hazard, a background zone is introduced and the seismicity rates in the background zone are calculated using smoothed-seismicity approach. The state-of-the-art SSC model presented here is the first fully documented and ready-to-use fault-based SSC model developed for the PSHA of Istanbul.

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Rost, S., G. A. Houseman, A. W. Frederiksen, D. G. Cornwell, M. Kahraman, S. Altuncu Poyraz, U. M. Teoman, et al. "Structure of the northwestern North Anatolian Fault Zone imaged via teleseismic scattering tomography." Geophysical Journal International 227, no. 2 (July 10, 2021): 922–40. http://dx.doi.org/10.1093/gji/ggab265.

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SUMMARY Information on fault zone structure is essential for our understanding of earthquake mechanics, continental deformation and seismic hazard. We use the scattered seismic wavefield to study the subsurface structure of the North Anatolian Fault Zone (NAFZ) in the region of the 1999 İzmit and Düzce ruptures using data from an 18-month dense deployment of seismometers with a nominal station spacing of 7 km. Using the forward- and back-scattered energy that follows the direct P-wave arrival from teleseismic earthquakes, we apply a scattered wave inversion approach and are able to resolve changes in lithospheric structure on a scale of 10 km or less in an area of about 130 km by 100 km across the NAFZ. We find several crustal interfaces that are laterally incoherent beneath the surface strands of the NAFZ and evidence for contrasting crustal structures either side of the NAFZ, consistent with the presence of juxtaposed crustal blocks and ancient suture zones. Although the two strands of the NAFZ in the study region strike roughly east–west, we detect strong variations in structure both north–south, across boundaries of the major blocks, and east–west, parallel to the strike of the NAFZ. The surface expression of the two strands of the NAFZ is coincident with changes on main interfaces and interface terminations throughout the crust and into the upper mantle in the tomographic sections. We show that a dense passive network of seismometers is able to capture information from the scattered seismic wavefield and, using a tomographic approach, to resolve the fine scale structure of crust and lithospheric mantle even in geologically complex regions. Our results show that major shear zones exist beneath the NAFZ throughout the crust and into the lithospheric mantle, suggesting a strong coupling of strain at these depths.

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Yavasoglu, H., M. N. Alkan, K. Aladogan, I. M. Ozulu, V. Ilci, M. Sahin, F. E. Tombus, I. Tiryakioglu, and S. O. Kıvrak. "DETERMINATION OF ASEISMIC DEFORMATION ON NORTH ANATOLIAN FAULT IN ISMETPASA AND DESTEK REGIONS USING GPS DATA, TURKEY." Bulletin of the Geological Society of Greece 50, no. 1 (July 27, 2017): 182. http://dx.doi.org/10.12681/bgsg.11718.

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The North Anatolian Fault Zone (NAFZ) is one of the most destructive fault in the eastern Mediterranean region. After Izmit and Düzce earthquakes, the projects on monitoring the fault motion increase using instrumental tools like GPS, InSAR, LIDAR, creepmeter, etc. The eastern and central part of the NAFZ from Karlıova to Vezirköprü has almost strike slip mechanism. The western part of the central NAFZ from Vezirköprü to Bolu has transpressive character. The aseismic fault deformation (creep) is also important phenomena for these two sections. The InSAR and LIDAR studies showed that the Ismetpasa and Destek regions have creep motions. For this purpose, the new project has been started to proof this phenomena with GPS data and to determine quantitatively the rate of convergence and its variation along segment of the NAF between Bolu and Çorum. The main aim of this study is determination of creep rate with geodetic measurements and combination of the data obtained from seismology, geodesy and geophysics to understand fault mechanism. Therefore, in this paper we discuss tectonic phenomena on the central part of the NAFZ and present the first results of the project.

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Kiratzi, A., C. Benetatos, and Z. Roumelioti. "Distributed earthquake focal mechanisms in the Aegean Sea." Bulletin of the Geological Society of Greece 40, no. 3 (June 5, 2018): 1125. http://dx.doi.org/10.12681/bgsg.16842.

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Nearly 2,000 earthquake focal mechanisms in the Aegean Sea and the surroundings for the period 1912- 2006, for 1.5 <M<7.5, and depths from 0 to 170 km, indicate a uniform distribution and smooth variation in orientation over wide regions, even for the very small magnitude earthquakes. ~ 60% of the focal mechanisms show normal faulting, that mainly strikes ~E-W. However, a zone ofN-S normal faulting runs the backbone of Albanides-Hellenides. Low-angle thrust and reverse faulting is confined in western Greece (Adria-Eurasia convergence) and along the Hellenic trench (Africa-Eurasia). In the central Aegean Sea the effect of the propagating tip of the North Anatolian Fault into the Aegean Sea is pronounced and strike-slip motions are widely distributed. Shearing does not cross central Greece. Strike-slip motions reappear in the Cephalonia-Lefkada Transform Fault zone and in western Péloponnèse, which shows very complex tectonics, with different types of faulting being oriented favourably and operating under the present stress-field. Moreover, in western Péloponnèse the sense of the observed shearing is not yet clear, whether it is dextral or sinistral, and this lack of data has significant implications for the orientation of the earthquake slip vectors compared to the GPS obtained velocity vectors.

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Najdahmadi, Bita, Pavla Hrubcová, Václav Vavryčuk, and Marco Bohnhoff. "Imaging the Mudurnu Segment of the North Anatolian Fault Zone From Waveforms of Small Earthquakes." Journal of Geophysical Research: Solid Earth 123, no. 1 (January 2018): 493–512. http://dx.doi.org/10.1002/2017jb015198.

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Karalar, Memduh, and Murat Çavuşli. "Evaluation of 3D Nonlinear Earthquake Behaviour of the Ilısu CFR Dam under Far-Fault Ground Motions." Advances in Civil Engineering 2019 (January 8, 2019): 1–15. http://dx.doi.org/10.1155/2019/7358710.

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In the recent times, many huge concrete face rockfill dams (CFRDs) have been modelled and constructed in the world, and many of these dams are located on the strong earthquake zones. Examination of the seismic behaviour of a CFR dam built on the seismic zone is very important to assess the safety and future of the dam. For this reason, the nonlinear earthquake behaviour of these dams should be constantly observed taking into account the seismicity of the zone. In this study, three-dimensional (3D) seismic behaviour of the Ilısu dam built on the East Anatolian Fault (EAF) line is examined considering the effect of the important various far-fault earthquakes. The 3D finite difference model of the Ilısu dam is created using the FLAC3D software based on the finite difference method. The dam body, foundation, and concrete slab constantly interact during the lifetime of the CFRDs. Therefore, the special interface elements are defined between the dam body, concrete slab, and foundation to represent the interaction condition. The Mohr–Coulomb nonlinear material model is used for the rockfill materials and foundation. Moreover, the concrete slab is modelled considering the Drucker–Prager nonlinear material model to represent the nonlinearity of the concrete. Very special seismic boundary conditions rarely used for CFR dams in the past are used in this work. These boundary conditions are free-field and quiet boundary conditions. The free-field boundary condition that is a very important boundary condition for the nonlinear seismic analyses is considered for the lateral boundaries of the 3D model. In addition, the quiet artificial boundary condition is used for the bottom of the foundation. While defining these boundary conditions, the special fish functions are created and defined to the software. Moreover, the hysteric damping coefficients are separately calculated for all of the materials. These special damping values are defined to the FLAC3D software using the special fish functions to capture the effects of the variation of the modulus and damping ratio with the dynamic shear-strain magnitude. In the numerical analyses, a total of 7 various strong far-fault earthquakes are used for the 3D nonlinear earthquake analyses, and 7 different numerical analyses are performed for the full-reservoir condition of the Ilısu CFR dam. According to the seismic results, the principal stresses for the three critical nodal points on the dam body surface are examined and evaluated in detail. It is clearly understood that the nonlinear seismic behaviour of the Ilısu dam changes depending on the magnitudes and periods of the far-fault earthquakes. Each far-fault earthquake has different seismic effects on the nonlinear principal stress behaviour of the Ilısu CFR dam.

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Durand, Virginie, Stephan Bentz, Grzegorz Kwiatek, Georg Dresen, Christopher Wollin, Oliver Heidbach, Patricia Martínez-Garzòn, Fabrice Cotton, Murat Nurlu, and Marco Bohnhoff. "A Two-Scale Preparation Phase Preceded an Mw 5.8 Earthquake in the Sea of Marmara Offshore Istanbul, Turkey." Seismological Research Letters 91, no. 6 (September 23, 2020): 3139–47. http://dx.doi.org/10.1785/0220200110.

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Abstract We analyze the spatiotemporal evolution of seismicity during a sequence of moderate (an Mw 4.7 foreshock and Mw 5.8 mainshock) earthquakes occurring in September 2019 at the transition between a creeping and a locked segment of the North Anatolian fault in the central Sea of Marmara, northwest Turkey. To investigate in detail the seismicity evolution, we apply a matched-filter technique to continuous waveforms, thus reducing the magnitude threshold for detection. Sequences of foreshocks preceding the two largest events are clearly seen, exhibiting two different behaviors: a long-term activation of the seismicity along the entire fault segment and a short-term concentration around the epicenters of the large events. We suggest a two-scale preparation phase, with aseismic slip preparing the mainshock final rupture a few days before, and a cascade mechanism leading to the nucleation of the mainshock. Thus, our study shows a combination of seismic and aseismic slip during the foreshock sequence changing the strength of the fault, bringing it closer to failure.

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Kuyuk, H. S., E. Yildirim, E. Dogan, and G. Horasan. "Application of k-means and Gaussian mixture model for classification of seismic activities in Istanbul." Nonlinear Processes in Geophysics 19, no. 4 (August 3, 2012): 411–19. http://dx.doi.org/10.5194/npg-19-411-2012.

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Abstract. Two unsupervised pattern recognition algorithms, k-means, and Gaussian mixture model (GMM) analyses have been applied to classify seismic events in the vicinity of Istanbul. Earthquakes, which are occurring at different seismicity rates and extensions of the Thrace-Eskisehir Fault Zone and the North Anatolian Fault (NAF), Turkey, are being contaminated by quarries operated around Istanbul. We have used two time variant parameters, complexity, the ratio of integrated powers of the velocity seismogram, and S/P amplitude ratio as classifiers by using waveforms of 179 events (1.8 < M < 3.0). We have compared two algorithms with classical multivariate linear/quadratic discriminant analyses. The total accuracies of the models for GMM, k-means, linear discriminant function (LDF), and quadratic discriminant function (QDF) are 96.1%, 95.0%, 96.1%, 96.6%, respectively. The performances of models are discussed for earthquakes and quarry blasts separately. All methods clustered the seismic events acceptably where QDF slightly gave better improvements compared to others. We have found that unsupervised clustering algorithms, for which no a-prior target information is available, display a similar discriminatory power as supervised methods of discriminant analysis.

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Oglesby, David D., and P. Martin Mai. "Fault geometry, rupture dynamics and ground motion from potential earthquakes on the North Anatolian Fault under the Sea of Marmara." Geophysical Journal International 188, no. 3 (January 13, 2012): 1071–87. http://dx.doi.org/10.1111/j.1365-246x.2011.05289.x.

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Drab, L., A. Hubert Ferrari, S. Schmidt, and P. Martinez. "The earthquake sedimentary record in the western part of the Sea of Marmara, Turkey." Natural Hazards and Earth System Sciences 12, no. 4 (April 27, 2012): 1235–54. http://dx.doi.org/10.5194/nhess-12-1235-2012.

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Abstract. The submarine part of the North Anatolian Fault (NAF) is a very significant hazard for the 12 million people living in Istanbul (Turkey). An accurate seismic risk assessment necessitates paleoseismological data, which can be retrieved in the Marmara Sea by using sedimentary cores. Here, a record of turbidites was obtained in five cores, spanning the Tekirdağ Basin, the Western High and the Central Basin linked by the Tekirdağ fault segment. The turbidites are synchronous at different sites across the two basins and through the structural high pointing to shaking by earthquakes as a triggering mechanism. In particular, the M = 7.4 1912 Mürefte earthquake left a distinctive sedimentary imprint in all the studied cores. Radiocarbon dating implies a turbidite recurrence interval of about 300 yr. The low number of seismo-turbidites documented in the Central Basin compared to the Tekirdağ Basin suggests quasi-synchronous ruptures of the Tekirdağ Segment and the adjacent Central Segment of the NAF or a partial seismic slip on the Central Segment. Both scenarios have implications regarding seismic hazard. Finally, though we obtained a paleoseismological record of the ruptures along the Tekirdağ Segment, further chronological constraints are needed to better date the events and to confirm the completeness of the obtained record.

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Benetatos, C., A. Kiratzi, K. Kementzetzidou, Z. Roumelioti, G. Karakaisis, E. Scordilis, I. Latoussakis, and G. Drakatos. "THE PSACHNA (EVIA ISLAND) EARTHQUAKE SWARM OF JUNE 2003." Bulletin of the Geological Society of Greece 36, no. 3 (January 1, 2004): 1379. http://dx.doi.org/10.12681/bgsg.16504.

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Evia Island (Greece) lies in a transition zone from strike-slip faulting in the east, due to the strands of the North Anatolian Fault (NAF) that enter to the Aegean Sea, to normal faulting in the west along central Greece. In June 2003 a series of moderate events occurred in central Evia whose source parameters are investigated. These earthquakes caused serious damage to almost 20 residencies mainly in the town of Psachna. The sequence could be identified as an earthquake swarm with earthquake magnitudes in the range of 3 < M < 4.9. We used the Ρ and S arrivals at the stations of the National Seismic Network to relocate the events using the double-difference algorithm. All Ρ and S phase pickings were made by us using the broad band records from the network operated by the Geodynamic Institute of Athens. The relocated epicenters define a pronounced ENE- WSW zone, parallel to the high topography of the area. All depths are shallow from 1 to 8 Km. Regional waveform modeling was applied to determine the focal mechanisms of the larger events and FPFIT for the focal mechanisms of the smaller magnitude events. The majority of the focal mechanisms indicate normal faulting along almost E-W striking planes suggesting that deformation is mainly taken by normal faulting with a minor dextral horizontal motion. Normal faults with a N-S strike have been also observed showing that the E-W extension is present as it is observed in other parts of the Aegean region. Evia Island and its pattern of deformation is very interesting from the seismotectonic point of view. The fact that no large magnitude earthquake has occurred in Evia Island during instrumental times, makes the study of this earthquake swarm important. Previous work (Kiratzi, 2002) has shown that the deformation in northern Evia Island is taken up mainly by strike-slip faulting. Moreover, depending on the orientation of the activated faults in respect to the present state stress field, dextral or sinistral horizontal motion is observed. The Psachna earthquakes showed that an almost N-S extensional field prevails in central Evia Island with a few strikeslip focal mechanisms, suggesting that this part is mostly affected by the normal faulting system of central Greece.

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Fraser, J., J. S. Pigati, A. Hubert-Ferrari, K. Vanneste, U. Avsar, and S. Altinok. "A 3000-Year Record of Ground-Rupturing Earthquakes along the Central North Anatolian Fault near Lake Ladik, Turkey." Bulletin of the Seismological Society of America 99, no. 5 (September 23, 2009): 2681–703. http://dx.doi.org/10.1785/0120080024.

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Avşar, Ulaş, Aurélia Hubert-Ferrari, Marc De Batist, Sabine Schmidt, and Nathalie Fagel. "Sedimentary records of past earthquakes in Boraboy Lake during the last ca 600 years (North Anatolian Fault, Turkey)." Palaeogeography, Palaeoclimatology, Palaeoecology 433 (September 2015): 1–9. http://dx.doi.org/10.1016/j.palaeo.2015.04.031.

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Hartleb, R. D., J. F. Dolan, O. Kozaci, H. S. Akyuz, and G. G. Seitz. "A 2500-yr-long paleoseismologic record of large, infrequent earthquakes on the North Anatolian fault at Cukurcimen, Turkey." Geological Society of America Bulletin 118, no. 7-8 (June 30, 2006): 823–40. http://dx.doi.org/10.1130/b25838.1.

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Janin, Alexandre, Mathieu Rodriguez, Dimitris Sakellariou, Vasilis Lykousis, and Christian Gorini. "Tsunamigenic potential of a Holocene submarine landslide along the North Anatolian Fault (northern Aegean Sea, off Thasos island): insights from numerical modelling." Natural Hazards and Earth System Sciences 19, no. 1 (January 16, 2019): 121–36. http://dx.doi.org/10.5194/nhess-19-121-2019.

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Abstract. The North Anatolian Fault in the northern Aegean Sea triggers frequent earthquakes of magnitudes up to Mw∼7. This seismicity can be a source of modest tsunamis for the surrounding coastlines with less than 50 cm height according to numerical modelling and analysis of tsunami deposits. However, other tsunami sources may be involved, like submarine landslides. We assess the severity of this potential hazard by performing numerical simulations of tsunami generation and propagation from a Holocene landslide (1.85 km3 in volume) identified off Thasos. We use a model coupling the simulation of the submarine landslide, assimilated to a granular flow, to the propagation of the tsunami wave. The results of these simulations show that a tsunami wave of water height between 1.10 and 1.65 m reaches the coastline at Alexandroupoli (58 000 inhabitants) 1 h after the triggering of the landslide. In the same way, tsunami waves of water height between 0.80 and 2.00 m reach the coastline of the Athos peninsula 9 min after the triggering of the landslide. Despite numerous earthquakes of Mw>7 and strong detrital input (on the order of 30 cm ka−1), only a few Holocene landslides have been recognized so far, asking for tsunami recurrence in this area.

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Hartleb, R. D. "A 2000-Year-Long Paleoseismologic Record of Earthquakes along the Central North Anatolian Fault, from Trenches at Alayurt, Turkey." Bulletin of the Seismological Society of America 93, no. 5 (October 1, 2003): 1935–54. http://dx.doi.org/10.1785/0120010271.

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Leroy, Suzanne A. G., Sonay Boyraz, and Alper Gürbüz. "High-resolution palynological analysis in Lake Sapanca as a tool to detect recent earthquakes on the North Anatolian Fault." Quaternary Science Reviews 28, no. 25-26 (December 2009): 2616–32. http://dx.doi.org/10.1016/j.quascirev.2009.05.018.

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Journal articles on the topic 'Anatolian Fault; Earthquakes'

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