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Finite-Fault Stochastic Simulation of the 2008 Iwate-Miyagi Nairiku, Japan, Earthquake
  • Jafar Zana Karashi,
  • Meghdad Samaei,
  • Masakatsu Miyajima
Jafar Zana Karashi
Azarbaijan Shahid Madani University

Corresponding Author:jafarkarashi@yahoo.com

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Meghdad Samaei
Allame Rafiei Institute of Higher Education
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Masakatsu Miyajima
Kanazawa University
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Finite-fault stochastic method was applied to simulate the Mw 6.9, 2008 Iwate-Miyagi earthquake at 44 selected Kik-net sites using EXSIM computer code. To investigate the effects of source characteristics on the simulated results, three models were considered: two models with prescribed slip distribution (Model 1 and Model 3) and a model with random slip distribution (Model 2). S-wave regional attenuation indicates obvious difference between fore-arc and back-arc regions which are formed by volcanic front. Site amplification was determined by corrected surface to borehole spectral ratio and Quarter wavelength methods. High frequency decay parameter (kappa) was estimated to be 0.0473 s. The value of 160 bars for stress drop was calculated by minimizing absolute residual of 5% damped pseudo spectral accelerations (PSA). Comparison of the observed and simulated peak ground accelerations and PSAs were performed to investigate the capability of our finite-fault models. The residual models represent that the simulated results by Model 2 are in good agreement with the observations in f < 3 Hz, while the other models can better simulate higher frequency motions. We also focused on the effects of slip patches sitting on the fault plane on near-field stations placed in the directions of slip propagation. For these stations, the simulated results by Model 1 and Model 3 were preferred over those of Model 2. Finite-fault models successfully interpreted the real forced motion to AKTH04 where the recorded peak values were abnormal for non-seismological reasons. Finally, the comparison of intensity measures with the GMPEs showed good agreement.