HR: 0800h
AN: S41B-0988    [Abstracts]
TI: Earthquake triggering along a segmented creeping fault: 1951 ML7.3 Hualien-Taitung earthquake sequence in eastern Taiwan
AU: * Chen, H
EM: l4890102@ccmail.ncku.edu.tw
AF: Department of Earth Sciences, National Cheng Kung University, No 1, Ta-Hsueh Rd, Tainan, R. O. C., Taiwan, Tainan, 704 Taiwan
AU: Toda, S
EM: s-toda@aist.go.jp
AF: Active Fault Research Center, Geological Survey of Japan, National Institute of Advanced Industrial Science and Technology (AIST) Site 7, 1-1-1 Higashi, Tsukuba, Ibaraki, 205-8567 Japan , Tsukuba, 205-8567 Japan
AU: Rau, R
EM: raurj@mail.ncku.edu.tw
AF: Department of Earth Sciences, National Cheng Kung University, No 1, Ta-Hsueh Rd, Tainan, R. O. C., Taiwan, Tainan, 704 Taiwan
AB: Understanding of fault interactions along active plate boundaries is significant for improving seismic hazard assessment. As the most destructive seismic episode even known in eastern Taiwan, the 1951 ML 7.3 Hualien­VTaitung (H-T), Taiwan earthquake series provide a good opportunity to study earthquake triggering processes along an arc-continent collision boundary. This sequence occurred at first on October 21, 1951 with the ML 7.3 Hualien earthquake located at the northernmost segment of the Longitudinal Valley Fault (LVF) and then triggered three ML >6 events with 10-40 km surface ruptures propagating southward. The first triggered November shock did not occur at the nearby Yuli fault segment but occurred at the ~100-km away creeping Chihshang fault. By calculation of static coulomb stress transfer with the rate/state stress transfer model, we modeled the temporal priority of encouraged rupture on four segments of the LVF. We found that rupture of the Hualien mainshock is unlikely to trigger the neighboring Yuli fault prior to the creeping Chihshang fault; doing so requires that both the Yuli and Chihshang segments having background aftershock duration of less than 2.5 years. We also found that the factor controlling the priority of large triggered events varies with static coulomb stress change loading on a given fault segment. When the loaded coulomb stress change is less than 0.5 bar, the priority is mostly governed by the seismicity rate. The segment with higher seismicity rate corresponds to faster triggering, which is consistent with our observations. When the loaded coulomb stress change larger than 0.5 bar, the aftershock duration plays an important role on the priority, the segment with longer aftershock duration leads to faster triggering. Modeling of the jumping behavior of the 1951 H-T sequence suggests that the along-strike rupture directivity depends on the location and magnitude of the mainshock and seismicity rate and aftershock decaying rate of individual fault segment, and can be explained by the rate/state stress transfer model.
DE: 7223 Earthquake interaction, forecasting, and prediction (1217, 1242)
DE: 7230 Seismicity and tectonics (1207, 1217, 1240, 1242)
DE: 8118 Dynamics and mechanics of faulting (8004)
SC: Seismology [S]
MN: Fall Meeting 2005