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Aochi, Hideo
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Aochi, Hideo
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10244449300
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- PublicationRestrictedPhysics‐Based Broadband Ground‐Motion Simulations for ProbableMw≥7.0 Earthquakes in the Marmara Sea Region (Turkey)(2017)
; ; ; ; ; ; ;; ; The city of Istanbul is characterized by one of the highest levels of seismic risk in the Mediterranean region. An important source of such increased risk is the high probability of large earthquake occurrence during the coming years, which stands at about 65% likelihood owing to the existing seismic gap and the post-1999 earthquake stress transfer at the western portion of the North Anatolian fault zone. In this study, we simulated hybrid broadband time histories from selected earthquakes having magnitude Mw >7:0 in the Sea of Marmara within 10–20 km of Istanbul, the most probable scenarios for simulated generation of the devastating 1509 event in this region. Physics-based rupture scenarios, which may be an indication of potential future events, are adopted to estimate the ground-motion characteristics and its variability in the region. Two simulation techniques are used to compute a realistic time series, considering generic rock site conditions. The first is a full 3D wave propagation method used for generating low-frequency seismograms, and the second is a stochastic finite-fault model approach based on dynamic corner-frequency high-frequency seismograms. Dynamic rupture is generated and computed using a boundary integral equation method, and the propagation in the medium is realized through a finite-difference approach. The results from the two simulation techniques are then merged by performing a weighted summation at intermediate frequencies to calculate a broadband synthetic time series. The simulated hybrid broadband ground motions are validated by comparing peak ground acceleration, peak ground velocity (PGV), and spectral accelerations (5% damping) at different periods with the ground-motion prediction equations in the region. Our simulations reveal strong rupture directivity and supershear rupture effects over a large spatial extent, which generate extremely high near-fault motions exceeding the 250 cm=s PGV along the entire length of the ruptured fault.995 9 - PublicationOpen AccessPerformance assessment of finite-fault inversion codes in the Marmara configuration”- “Near-Real time estimation of most relevant earthquake source parameters(2015-04-30)
; ; ; ; ; ;Cirella, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Piatanesi, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Diao, F. ;Wang, R. ;Aochi, H.; ; ; ;102 477 - PublicationOpen AccessComparison of ground motion hybrid simulations to NGA modified GMPE in the Marmara Sea region (Turkey) in a directivity rupture context.(2016-12)
; ; ; ; ; ; ; ; ; ; ; We have simulated strong ground motions for two Mw>7.0 rupture scenarios on the North Anatolian Fault, in the Marmara Sea within 10-20 km of Istanbul. This city is characterized by one of the highest levels of seismic risk in Europe and the Mediterranean region. The increased risk in Istanbul is due to the high probability of the occurrence of a large earthquake, which stands at about 65% during the coming years. To estimate the ground motion characteristics and its variability in the region we have adopted physics-based rupture scenarios, simulating hybrid broadband time histories. We have merged two simulation techniques: a full 3D wave propagation method to generate low-frequency seismograms (Aochi and Ulrich, 2015) and the stochastic finite-fault model approach based on a dynamic corner frequency (Motazedian and Atkinson, 2005) to simulate high-frequency seismograms. They are merged to compute realistic broad band hybrid time series. The comparison of intensity measures (PGA, PGV, SA) on our simulations with recently proposed Ground Motion Prediction Equations (GMPEs) in the region (Boore & Atkinson, 2008; Chiou & Young, 2008; Akkar & Bommer, 2010; Akkar & Cagnan, 2010) points out the rupture directivity and super-shear rupture effects associated to these cases. In order to improve the comparison, we use the GMPE proposed by Boore & Atkinson (2008) with the directivity correction proposed by Spudich & Chiu (2008). This study highlights the importance of the directivity of the rupture for the hazard estimation in the region of the Marmara Sea and especially for the city of Istanbul.118 27