Tectonic setting of the southern Marmara Sea region: based on seismic reflection data and gravity modelling

Adatepe, Fatih; Demirel, Sinan; Alpar, Bedri

doi:10.1016/s0025-3227(02)00355-9

Cited by 19 publications

(16 citation statements)

References 13 publications

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“…Several multidisciplinary studies that consider the joint analysis of magnetic and gravity fields, electrical and magnetotelluric measurements (e.g., Honkura et al, 1985;Honkura and Isikara, 1991;Honkura et al, 2000) have revealed clear anomalous zones related to the variability of the extent of fracturing in different segments of the NAFZ. Similar features were identified by the analysis of the results of the combined modeling of gravity and reflection seismic data collected in the Marmara Sea region (Adatepe et al, 2002). Other active source seismic investigations of the Marmara Sea and surrounding areas (Smith et al, 1995;Okay et al, 2000;Yaltirak and Alpar, 2002;Demirbag et al, 2003;Karabulut et al, 2003;Carton et al, 2007) provided evidence for signatures of active faults, resulting in a detailed structure of the sedimentary cover in the pull-apart basins located in the western end of the NAFZ.…”

Section: Introductionsupporting

confidence: 59%

Distribution of Seismic Velocities and Attenuation in the Crust beneath the North Anatolian Fault (Turkey) from Local Earthquake Tomography

Koulakov¹,

Bindi²,

Parolai³

et al. 2010

Bulletin of the Seismological Society of America

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We investigate the crustal structure beneath the western part of the North Anatolian fault zone (NAFZ), an area where at least five damaging earthquakes occurred during the twentieth century. This study is based on local earthquake tomography using the data from aftershocks of the Izmit event (17 August 1999, M 7:4) recorded by stations of permanent and temporary networks. We derive the distribution of V P , V S , and the V P =V S ratio based on the iterative inversion for both V P V S and V P V P =V S using the LOTOS code. Innovatively, in this study we perform an inversion for frequency-dependent S-wave attenuation (1=Q S ). The reliability of the results is assessed through synthetic tests. The distributions of the resulting seismic parameters (V P , V S , V P =V S , and Q S ) highlight important geodynamical features in the study area. The low-velocity and high-attenuation patterns mostly correlate with the fracturing zones of the NAFZ. Low velocities are also observed beneath the main sedimentary basins (e.g., Adapazarı, Düzce, and Kuzuluk). High-velocity and lowattenuation patterns correlate with blocks presumed to be rigid (Kocaeli, Armutlu, and Almacik blocks). The rupture traces of the largest earthquakes in this area pass generally in the transition areas between high and low velocities, while moderate and weak seismicity is mostly concentrated in low-velocity areas. Based on these results we propose and discuss the role that the Almacik block could have played in producing the largest earthquakes in the study area in the twentieth century.

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Section: Introductionsupporting

confidence: 59%

Distribution of Seismic Velocities and Attenuation in the Crust beneath the North Anatolian Fault (Turkey) from Local Earthquake Tomography

Koulakov¹,

Bindi²,

Parolai³

et al. 2010

Bulletin of the Seismological Society of America

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“…Here we compare our results with several gravity profiles available for the Marmara Sea region (Adatepe et al, 2002;Ozer et al, 2001;and Ateş et al, 2003). The locations of the profiles are shown in Fig.…”

Section: Interpretations With Particular Reference To Other Observationsmentioning

confidence: 74%

“…We estimated the velocity perturbation along the gravity profiles by interpolating our velocity perturbation data at each grid point, as shown in Figs. 13, 14, and 15 for Adatepe et al (2002), Özer et al (2001) and Ateş et al (2003), respectively. Adatepe et al (2002) found low gravity values for the Miocene-Pliocene sedimentary sequences and higher values for the regions uplifted by deformation.…”

Section: Interpretations With Particular Reference To Other Observationsmentioning

confidence: 92%

“…Neotectonic and paleoseismological studies on several segments of the NAFZ provided new quantitative information about the tectonic process and the time record of major earthquakes (Ikeda et al, 1989;Barka, 1992). Some other geophysical observations such as gravity, magnetotellurics (MT) and the magnetic field have also been undertaken Işikara et al, 1985;Tunçer et al, 1991a, b;Honkura and Işikara, 1991;Gürer, 1996;Honkura et al, 2000;Adatepe et al, 2002;Tank et al, 2003;Ateş et al, 2003). Most of these studies are directed toward the understanding of shallow structures associated with active faults rather than the seismogenic zones which are supposed to be located between 7 and 15 km in depth, and hence the information on the deeper structure is still insufficient.…”

Section: Introductionmentioning

confidence: 99%

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Three-dimensional structure of Vp, Vs and Vp/Vs in the upper crust of the Marmara region, NW Turkey

et al. 2005

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We applied a 3-D seismic tomography inversion algorithm to arrival-time data obtained, during 18 years from 1985 to 2002, from local seismic networks and aftershock studies in the Marmara region, in order to better understand the upper crustal structure of the complex tectonic region. We integrated all the available data set into a common data set and relocated the events, using a 1-D velocity model. We then selected 3,949 earthquakes and obtained 92355 arrival times, in total, consisting of 59,313 P-wave and 33,042 S-wave arrival times. In this paper we present detailed crustal structures for V p, V s and V p/V s ratios from the surface down to 15 km depth with good resolution in terms of the hit count analysis of seismic rays, the checkerboard and restoring resolution tests for the studied region. The results obtained from the inversion suggest that the western part of the North Anatolian Fault Zone shows strong lateral heterogeneity. We concluded that no clear pattern exists between the distribution of microearthquakes and aftershocks and the velocity perturbations presented in this paper. This is probably due to complex tectonic and geological structures. Large coseismic slip associated with the two recent strong earthquakes was found to correspond to higher velocity anomalies, as was often found recently. On the other hand, low velocity values correspond to the sedimentary units or the alluvium regions, as supported by the low resistivity and gravity values. Thus the results presented in this paper are quite consistent with the other data such as gravity, resistivity and magnetic anomalies, indicating that our model is reliable and efficient and it should be useful for further interpretation of tectonic and geological problems in this region. It should be pointed out, however, that the results of S-wave perturbations and V p/V s ratio could not be discussed in detail because of insufficient quality of the S-wave data and the reliability of the results is not very high. Nonetheless, the fact that recent large Izmit earthquake and moderate aftershocks that occurred in or around the high velocity zones near the low velocity region suggests that high velocity regions found in the area close to Istanbul in the Marmara Sea and also at the Iznik-Mekece fault are potential sites for strain energy accumulation and release.

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“…Furthermore, joint analysis of magnetic and gravity fields, electrical and magnetotelluric measurements (Honkura et al 1985;Honkura and Isikara 1991;Honkura et al 2000) has revealed clear anomalous zones related to the variability of the extent of fracturing in different segments of the NAF. Similar features were also found by the analysis of the results of the combined modeling of gravity and reflection seismic data collected in the Marmara Sea region (Adatepe et al 2002). The crustal seismic structure in the western part of the NAF was investigated by different research groups (e.g., Gurbuz et al 2000;Nakamura et al 2002;Baris et al 2005;Salah et al 2007) using several tomographic studies.…”

Section: Introductionmentioning

confidence: 53%

Investigating P- and S-wave velocity structure beneath the Marmara region (Turkey) and the surrounding area from local earthquake tomography

2016

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We investigated the crustal structure beneath the Marmara region and the surrounding area in the western part of the North Anatolian fault zone. These areas have high seismicity and are of critical significance to earthquake hazards. The study was based on travel-time tomography using local moderate and micro-earthquakes occurring in the study area recorded by the Multi-Disciplinary Earthquake Research in High Risk Regions of Turkey project and Kandilli Observatory and Earthquake Research Institute. We selected 2131 earthquakes and a total of 92,858 arrival times, consisting of 50,044 P-wave and 42,814 S-wave arrival times. We present detailed crustal structure down to 50 km depth beneath the Marmara region for P-and S-wave velocities using the LOTOS code based on iterative inversion. We used the distributions of the resulting seismic parameters (Vp, Vs) to pick out significant geodynamical features. The high-velocity anomalies correlate well with fracturing segments of the North Anatolian fault. High seismicity is mostly concentrated in these segments. In particular, low velocities were observed beneath the central Marmara Sea at 5 km depth.

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Tectonic setting of the southern Marmara Sea region: based on seismic reflection data and gravity modelling

Cited by 19 publications

References 13 publications

Distribution of Seismic Velocities and Attenuation in the Crust beneath the North Anatolian Fault (Turkey) from Local Earthquake Tomography

Distribution of Seismic Velocities and Attenuation in the Crust beneath the North Anatolian Fault (Turkey) from Local Earthquake Tomography

Three-dimensional structure of Vp, Vs and Vp/Vs in the upper crust of the Marmara region, NW Turkey

Investigating P- and S-wave velocity structure beneath the Marmara region (Turkey) and the surrounding area from local earthquake tomography

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