HR: 0800h
AN: S21B-0211    [Abstracts]
TI: Strong Ground Motion Simulation in Fukuoka Region (Japan) Using Finite-fault Stochastic Simulation Method of the March 20, 2005 Earthquake.
AU: * Moustafa, S S
EM: moustafa@geo.kyushu-u.ac.jp
AF: Hiroshi Takenaka, Department of Earth and Planetary Science, Fukuoka, 812-0053 Japan
AU: Ohshima, M
EM: kouki@geo.kyushu-u.ac.jp
AF: Hiroshi Takenaka, Department of Earth and Planetary Science, Fukuoka, 812-0053 Japan
AU: Takenaka, H
EM: takenaka@geo.kyushu-u.ac.jp
AF: Hiroshi Takenaka, Department of Earth and Planetary Science, Fukuoka, 812-0053 Japan
AU: Kawase, H
EM: kawase@arch.kyushu-u.ac.jp
AF: Hiroshi Kawase, Department of Human-Environmental Studies, Fukuoka, 812-0053 Japan
AB: Stochastic finite-fault simulation (Beresnev and Atkinson, 1998) is used to simulate the acceleration records of West off Fukuoka earthquake which took place on March 20, 2005, at 10:53 (JST) with Mw 6.6 at a depth of 10 km off-shore west of Fukuoka prefecture, Japan. Stochastic simulations are generated for finite-fault ruptures, in order to define the shape and amplitude level of the Fourier spectrum. The orientation of the fault model used in the present study is assumed to be strike of N 304 E with the dip angle of 87 degree (Takenaka et. al., 2005). The dimensions of the fault are chosen based on the spatial distribution of the aftershocks and the fault plane modeled with an array of subfaults. A slip distribution model, derived from previous studies of this earthquake, is used to specifically account for the source effect. The radiation from each subfault is modeled as Brune`s point source using the Omega square stochastic model approach. The earthquake rupture initiates at the hypocenter, and propagates in all directions along the fault plane. Simulations are generated for an observation point by summing the subfault time series, appropriately lagged in time. This approach is expedient and therefore cost-effective, and has been extensively used in the past by engineers (using empirical spectra) and recently by seismologists (using spectra derived from physical models of the source). The method is calibrated against its ability of reproducing the main shock recordings at 27 stations from K- and Kik-nets, NIED strong-motion stations, at epicentral distances ranging from 23 to 92 km. The intent of this presentation is to capture the essential characteristics of high-frequency motion at each site. The results show a satisfactory match between simulated and observed peak ground accelerations and Fourier spectra except some stations which suffered strong effects of the forward rupture directivity. Large differences between the synthetics and recordings are basically limited to the low-frequency part of the spectrum (less than 2 Hz) which imply that the discrepancies patterns between observed and recorded time histories of the 2005 West off Fukuoka earthquake may be explained by the destructive combination of the source directivity and the site effects.
DE: 7200 SEISMOLOGY
DE: 7212 Earthquake ground motions and engineering seismology
SC: Seismology [S]
MN: Fall Meeting 2005