HR: 1340h
AN: S43A-1047    [Abstracts]
TI: Dynamic rupture process of the 2004 Mid Niigata prefecture earthquake
AU: * MIYATAKE, T
EM: miyatake@eri.u-tokyo.ac.jp
AF: Earthquake Research Institute, University of Tokyo, Yayoi, 1-1-1, Bunkyo, Tokyo, 113-0032 Japan
AU: KIMURA, T
EM: tkimura@eri.u-tokyo.ac.jp
AF: Earthquake Research Institute, University of Tokyo, Yayoi, 1-1-1, Bunkyo, Tokyo, 113-0032 Japan
AU: YASUDA, T
EM: tyasuda@eri.u-tokyo.ac.jp
AF: Earthquake Research Institute, University of Tokyo, Yayoi, 1-1-1, Bunkyo, Tokyo, 113-0032 Japan
AB: We investigate a dynamic rupture process of the 2004 Mid Niigata prefecture, Japan, earthquake. Several kinematic models, i.e., space-time distributions of the fault motion, had been proposed for the earthquake. We carefully investigated those models, and have chosen the model by Hikima and Koketsu (2005) in which the proper crustal structure models were estimated by using waveform inversion of aftershocks before their source inversion. They also used enough duration of time windows of waveform inversion and the propagation speed of the window are fast enough for our detection of heterogeneity of onset time. We studied carefully the resultant kinematic slip rate time functions of the subfault. The onset time of the function seem to be delayed at several subfaults. We found that these subfaults correspond to negative stress drop regions with a few exceptions. The stress drop distribution was estimated from the kinematic slip model by using Okada_fs (1992) Green_fs function. In dynamic model, the delay of rupture corresponds to the high peak stress for a given stress drop distribution. Our dynamic model shows that the high peak stress and high fracture energy appears on the edge of the asperity and around the region with low rupture velocity. These distributions seem very reasonable since high peak stress drop accelerates rupture propagation and high peak stress decelerates it. We also calculated nearfield waveforms and found that the above delay of rupture is necessary for the waveform fitting. So these distribution causing to the delay of rupture are qualitatively validated. The study estimated fault macroscopic parameters and might provide data to consider the relationship between macroscopic and microscopic fault model.
DE: 7209 Earthquake dynamics (1242)
SC: Seismology [S]
MN: Fall Meeting 2005