HR: 17:30h
AN: S52K-07    [PDF]
TI: The Miyagi-ken-hokubu, Japan, earthquake, 2003 July 26 and its the largest fore-shock and largest after-shock
AU: * Yagi, Y
EM: yagi@kenken.go.jp
AF: IISEE, Building Research Institute, 1 Tachihara, Tsukuba, 3050802 Japan
AU: Ito, Y
EM: yito@bosai.go.jp
AF: National Research Institute for Earth Science and Disaster Prevention, 3-1 Tennodai, Tsukuba, 3050802 Japan
AB: On the morning of July 26, 2003, a destructive earthquake (Ms 6.1) struck Miyagi-ken, northeastern Japan. More then 600 people were injured mainly by fallen furnitures. The moment tensor determined by NIED shows a reverse-faulting with P-axis rotated slightly counterclockwise from the maximum compressive stress axis of the tectonic stress northern Japan. The moment tensor for the largest fore-shock (Ms 5.5) and the largest after-shock (Ms 5.4) show reverse faulting, while the strike directions for those three large earthquakes are different from each other. In this study, we apply a joint inversion (Yagi et al., 2003) for both strong ground motion and teleseismic body wave data to study the source process for the largest fore-shock, the main-shock, and largest after-shock. We use 3-component acceleration data recorded at 8 K-net stations, and vertical component teleseismic P-waveform data recorded at 7 stations provided by IRIS-DMC. Applying a multi-time window inversion to above data set, we determined spatial and temporal distribution of fault slip. To get stable and better resolution for rupture model, we incorporated prior information into observed data, and determined the optimal relative weights of information from the observed data and prior constraints using an optimized ABIC. We found that the sites for the largest fore-shock, the main-shock, and the largest after-shock are partitioning, which suggest three fault segments ruptured, separately. The P-axis of the fore-shock is consistent with the maximum compressive stress axis for tectonic stress, while P-axis for the main-shock and largest after-shock rotated counterclockwise form the maximum compressive stress. Our results suggest a sequence of fault motions as follows. The main-shock started the edge of fore-shock rupture area, and the largest aftershock started in northern side of main-shock, where the rupture of the mian-shock terminated.
UR: http://iisee.kenken.go.jp/staff/yagi
DE: 7200 SEISMOLOGY
DE: 7209 Earthquake dynamics and mechanics
DE: 7215 Earthquake parameters
SC: Seismology [S]
MN: 2003 Fall Meeting