A study of microearthquake seismicity and focal mechanisms within the Sea of Marmara (NW Turkey) using ocean bottom seismometers (OBSs)

Sato, Toshinori; Kasahara, Junzo; Taymaz, Tuncay; Ito, Masakazu; Kamimura, Atsushi; Hayakawa, Tadaaki; Tan, Onur

doi:10.1016/j.tecto.2004.07.018

Cited by 70 publications

(62 citation statements)

References 21 publications

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“…In each case, one of the nodal planes was parallel to the strike of the active faults, and we consider the present activity to reflect the crustal motion that caused these major earthquakes. The obtained distribution of focal mechanisms is mostly consistent with the tectonics and stress field in this region as reported by previous studies (Kiratzi 2002;Pinar et al 2003;Sato et al 2004;Örgülü 2011).…”

Section: Cmt Distributions Beneath the Sea Of Marmarasupporting

confidence: 91%

“…The presence of a normal fault is consistent with a tensional stress field caused by the crustal opening due to the pull-apart. Although no normal fault earthquakes have yet been reported around the WH (Kiratzi 2002;Pinar et al 2003;Sato et al 2004;Örgülü 2011Örgülü ), Yamamoto et al (2015 identified several earthquakes that are consistent with pull-apart activity by using intensive OBS observations. They also identified strike-slip earthquakes in this region.…”

Section: Discussionmentioning

confidence: 99%

“…However, precise hypocenter determinations made using ocean-bottom seismometers (OBSs) also provide detailed information about fault geometries and activities (e.g., Sato et al 2004;Yamamoto et al 2015), and studies of earthquake focal mechanisms have also revealed fault geometries and stress fields around the SOM (Kiratzi 2002;Pinar et al 2003;Sato et al 2004;Örgülü 2011Örgülü ). Hébert et al (2005 used information about the fault geometry of the NAF beneath the SOM to investigate the tsunami potential around the city of Istanbul, because damaging tsunamis have been triggered by historical earthquakes beneath the SOM.…”

Section: Introductionmentioning

confidence: 99%

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Focal mechanism determinations of earthquakes along the North Anatolian fault, beneath the Sea of Marmara and the Aegean Sea

Citak

Kalafat

2015

Earth Planet Sp

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We determined the centroid moment tensor (CMT) solutions of earthquakes that occurred along the North Anatolian fault (NAF) beneath the Sea of Marmara and the Aegean Sea, using data obtained from Turkey's broadband seismograph network. The CMT solution of the 2014 Aegean Sea earthquake (Mw 6.9) represents a strike-slip fault, consistent with the geometry of the NAF, and the source-time function indicates that this event comprised several distinct subevents. Each subevent is considered to have ruptured a different fault segment. This observation indicates the existence of a mechanical barrier, namely a NAF segment boundary, at the hypocenter. CMT solutions of background seismicity beneath the Aegean Sea represent strike-slip or normal faulting along the NAF or its branch faults. The tensional axes of these events are oriented northeast-southwest, indicating a transtensional tectonic regime. Beneath the Sea of Marmara, the CMT solutions represent mostly strike-slip faulting, consistent with the motion of the NAF, but we identified a normal fault event with a tensional axis parallel to the strike of the NAF. This mechanism indicates that a pull-apart basin, marking a segment boundary of the NAF, is developing there. Because ruptures of a fault system and large earthquake magnitudes are strongly controlled by the fault system geometry and fault length, mapping fault segments along NAF can help to improve the accuracy of scenarios developed for future disastrous earthquakes in the Marmara region.

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Section: Cmt Distributions Beneath the Sea Of Marmarasupporting

confidence: 91%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Focal mechanism determinations of earthquakes along the North Anatolian fault, beneath the Sea of Marmara and the Aegean Sea

Citak

Kalafat

2015

Earth Planet Sp

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“…Together with seismological and seismotectonic studies (Gürbüz et al 2000;Oncel and Wyss 2001;Oncel and Wilson 2006;Kalafat et al 2011), recent GPS and kinematic studies (Meade et al 2002;Flerit et al 2003) have indicated that the northern branch of the NAFZ is more active and also creates much larger motion than the southern branch. This hypothesis has also been verified by historical period (Ambraseys and Jackson 2000;Ambraseys 2001aAmbraseys , b, 2002a, instrumental period (Kalafat et al 2011), and recent detailed microearthquake seismicity studies (Sato et al 2004;Bohnhoof et al 2013). The northern branch of the NAFZ in the Sea of Marmara, extending for more than 150 km, has been identified as a seismic gap because it has not generated a strong earthquake during the earthquake series of the last century (Bohnhoof et al 2013).…”

Section: Introductionmentioning

confidence: 80%

Physically based probabilistic seismic hazard analysis using broadband ground motion simulation: a case study for the Prince Islands Fault, Marmara Sea

et al. 2016

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The main motivation for this study was the impending occurrence of a catastrophic earthquake along the Prince Island Fault (PIF) in the Marmara Sea and the disaster risk around the Marmara region, especially in Istanbul. This study provides the results of a physically based probabilistic seismic hazard analysis (PSHA) methodology, using broadband strong ground motion simulations, for sites within the Marmara region, Turkey, that may be vulnerable to possible large earthquakes throughout the PIF segments in the Marmara Sea. The methodology is called physically based because it depends on the physical processes of earthquake rupture and wave propagation to simulate earthquake ground motion time histories. We included the effects of all considerable-magnitude earthquakes. To generate the high-frequency (0.5-20 Hz) part of the broadband earthquake simulation, real, small-magnitude earthquakes recorded by a local seismic array were used as empirical Green's functions. For the frequencies below 0.5 Hz, the simulations were obtained by using synthetic Green's functions, which are synthetic seismograms calculated by an explicit 2D/3D elastic finite difference wave propagation routine. By using a range of rupture scenarios for all considerablemagnitude earthquakes throughout the PIF segments, we produced a hazard calculation for frequencies of 0.1-20 Hz. The physically based PSHA used here followed the same procedure as conventional PSHA, except that conventional PSHA utilizes point sources or a series of point sources to represent earthquakes, and this approach utilizes the full rupture of earthquakes along faults. Furthermore, conventional PSHA predicts ground motion parameters by using empirical attenuation relationships, whereas this approach calculates synthetic seismograms for all magnitudes of earthquakes to obtain ground motion parameters. PSHA results were produced for 2, 10, and 50 % hazards for all sites studied in the Marmara region.

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“…A complete understanding of the historical and instrumental seismicity, tectonics, geology, paleoseismology, and other neotectonic properties of the considered region are necessary for an ideal delineation of seismic source zones. Microseismicity and seismotectonics of the eastern part of the Marmara Sea, have been discussed by several researchers following the 1999 Izmitearthquake (e.g., [14,16,17,[31][32][33][34][35][36][37][38][39][40][41][42][43][44][45]). Using all available research results, earthquake epicenters from 2000 to 2014, with a magnitude greater than Mw ≥ .…”

Section: Data Processingmentioning

confidence: 99%

Spatial Analysis of b-value Variability in Armutlu Peninsula (NW Turkey)

Yeken

2016

Open Geosciences

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Spatial variations of b values were studied by means of 2376 earthquakes with a magnitude completeness of 2.7 in the Armutlu Peninsula (NW Turkey) during a 15-year period following the destructive earthquake on August 17, 1999 in Kocaeli. The b value of L6 for the entire Armutlu Peninsula represents a large value for a global value, but this analysis suggested that the distribution of b value around the Armutlu Peninsula varied extensively from 1.2 to 2.6. Several pockets of high bvalue re ected changes in the physical properties of the Armutlu Peninsula. The southern part of the peninsula represents a lower b value against the northern part of the peninsula. A high bvalue was observed around Termal and Armutlu towns where plenty of geothermal springs occur. Seismic tomography studies revealed a low velocity zone beneath the Termal area where the high b value was imaged in this study. A seismic swarm which is considered to be related with geothermal activity also occurred in 2014 at the same place. This observation suggests that it is possible to propose that the high b value in the northern part of the peninsula could be related to hydrothermal/geothermal activity which contributes to lowering the e ective stress.

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A study of microearthquake seismicity and focal mechanisms within the Sea of Marmara (NW Turkey) using ocean bottom seismometers (OBSs)

Cited by 70 publications

References 21 publications

Focal mechanism determinations of earthquakes along the North Anatolian fault, beneath the Sea of Marmara and the Aegean Sea

Focal mechanism determinations of earthquakes along the North Anatolian fault, beneath the Sea of Marmara and the Aegean Sea

Physically based probabilistic seismic hazard analysis using broadband ground motion simulation: a case study for the Prince Islands Fault, Marmara Sea

Spatial Analysis of b-value Variability in Armutlu Peninsula (NW Turkey)

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