HR: 1340h
AN: S53A-1078    [Abstracts]
TI: A Possible Mechanism of Variation in Size and Recurrence Intervals of Great Interplate Earthquakes along the Nankai Trough, Southwest Japan
AU: * Hori, T
EM: horit@jamstec.go.jp
AF: Institute for Research on Earth Evolution, Japan Agency for Marine-Earth Science and Technology, 3173-25, Showa-machi, Kanazawa-ku, Yokohama, 236-0001 Japan
AU: Kodaira, S
EM: kodaira@jamstec.go.jp
AF: Institute for Research on Earth Evolution, Japan Agency for Marine-Earth Science and Technology, 3173-25, Showa-machi, Kanazawa-ku, Yokohama, 236-0001 Japan
AU: Baba, T
EM: babat@jamstec.go.jp
AF: Institute for Research on Earth Evolution, Japan Agency for Marine-Earth Science and Technology, 3173-25, Showa-machi, Kanazawa-ku, Yokohama, 236-0001 Japan
AU: Sakaguchi, H
EM: sakaguchih@jamstec.go.jp
AF: Institute for Research on Earth Evolution, Japan Agency for Marine-Earth Science and Technology, 3173-25, Showa-machi, Kanazawa-ku, Yokohama, 236-0001 Japan
AU: Kaneda, Y
EM: kaneday@jamstec.go.jp
AF: Institute for Research on Earth Evolution, Japan Agency for Marine-Earth Science and Technology, 3173-25, Showa-machi, Kanazawa-ku, Yokohama, 236-0001 Japan
AB: Great interplate earthquakes have occurred repeatedly along the Nankai Trough. The recurrence interval and size have changed in each cycle. Although the variation in size and recurrence time is usually interpreted as a random phenomenon, for recent some cycles the recurrence intervals and earthquake sizes become smaller in time. However this pattern may happen by chance, we propose here a possible mechanism of this occurrence pattern based on numerical simulations of multiple earthquake cycles. We conducted numerical simulations of earthquake cycles assuming that the stress change caused by slip deficit and the frictional stress change acting on the plate boundary are equal. A friction law derived from laboratory experiments is used. The heterogeneous plate convergence rate and frictional properties are introduced based on the results of GPS data analysis and seismic structural surveys. Especially, some barriers whose fracture energy is larger than surrounding area are assumed in order to model the structural heterogeneities such as a subducted ridge. Significant variation in size and recurrence interval is found only when large characteristic slip distance anomaly is introduced in the deeper part of seismogenic zone. This causes incomplete stress release in and around the barriers. Since the rupture initiation point is near one of the barriers off Kii peninsula, accumulated stress remains there after an earthquake and rupture initiation timing of a following earthquake becomes earlier. The size of the following event should become smaller because stress is released completely in the main slip area far from the barriers and lower stress can be accumulated there during shorter time interval until the following event. This model also suggests that accumulated stress in and around the barriers should be released within several earthquake cycles. As a result, a significantly large earthquake occurs and most of the accumulated stress in the whole seismogenic zone is released.
DE: 7209 Earthquake dynamics (1242)
DE: 7230 Seismicity and tectonics (1207, 1217, 1240, 1242)
DE: 8163 Rheology and friction of fault zones (8034)
SC: Seismology [S]
MN: Fall Meeting 2005