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日時：7月29日（水）15:00〜 １時間程度
場所：京都大学宇治キャンパス 地震予知研究センター新館セミナー室(200)
タイトル：States of local stresses in the Sea of Marmara through the analysis of large numbers of small earthquakes
講演者： Yasemin Korkusuz Öztürk
要旨：
We invert the present day states of stresses for five apparent earthquake clusters in the northern branch of the North Anatolian Fault in the Sea of Marmara. As the center of the Sea of Marmara is prone to a devastating earthquake within a seismic gap between these selected clusters, sensitive analyses of the understanding of the stress and strain characteristics of the region are all-important. We use high quality P and S phases, and P-wave first motion polarities from 398 earthquakes with ML≥1.5 using at least 10 P-wave first motion polarities, and a maximum of 1 inconsistent station, obtained from a total of 105 seismic stations, including 5 continuous OBSs. We report here on large numbers of simultaneously determined individual fault plane solutions (FPSs), and orientations of principal stress axes, which previously have not been determined with any confidence from the basins of the Sea of Marmara and prominent fault branches.
We find out NE-SW trending transtensional stress structures, predominantly in the Eastern Tekirdağ basin, Eastern Çınarcık basin, Yalova and Gemlik clusters. We infer that a dextral strike-slip deformation exist in the Eastern Ganos Offshore cluster. Furthermore, we analyze FPSs of four ML≥4.0 earthquakes, occurred in seismically quiet regions after 1999 Izmit earthquake. Stress tensor solutions from a cluster of small events that we obtained, correlate with FPSs of these moderate size events as a demonstration of the effectiveness of the small earthquakes in the derivation of states of local stresses. Consequently, our analyses of seismicity and a large number of FPSs using the densest seismic network of Turkey contribute to better understanding of the present states of the stresses and seismotectonics of the Sea of Marmara.
Title: States of local stresses in the Sea of Marmara through the analysis of large numbers of small earthquakes
Lecturer: Yasemin Korkusuz Öztürk
Date: July 29, 15:00-
Place: Room 200, Research Center for Earthquake Prediction , Kyoto University Uji Campus
*Abstract:*
We invert the present day states of stresses for five apparent earthquake clusters in the northern branch of the North Anatolian Fault in the Sea of Marmara. As the center of the Sea of Marmara is prone to a devastating earthquake within a seismic gap between these selected clusters, sensitive analyses of the understanding of the stress and
strain characteristics of the region are all-important. We use high quality P and S phases, and P-wave first motion polarities from 398 earthquakes with ML≥1.5 using at least 10 P-wave first motion polarities, and a maximum of 1 inconsistent station, obtained from a
total of 105 seismic stations, including 5 continuous OBSs. We report here on large numbers of simultaneously determined individual fault plane solutions (FPSs), and orientations of principal stress axes, which previously have not been determined with any confidence from the basins of the Sea of Marmara and prominent fault branches.
We find out NE-SW trending transtensional stress structures, predominantly in the Eastern Tekirdağ basin, Eastern Çınarcık basin, Yalova and Gemlik clusters. We infer that a dextral strike-slip deformation exist in the Eastern Ganos Offshore cluster. Furthermore, we analyze FPSs of four ML≥4.0 earthquakes, occurred in seismically quiet regions after 1999 Izmit earthquake. Stress tensor solutions from a cluster of small events that we obtained, correlate with FPSs of these moderate size events as a demonstration of the effectiveness of the small earthquakes in the derivation of states of local stresses.
Consequently, our analyses of seismicity and a large number of FPSs using the densest seismic network of Turkey contribute to better understanding of the present states of the stresses and seismotectonics of the Sea of Marmara.
© Research Center for Earthquake Hazards.
© Research Center for Earthquake Hazards.
