HR: 1340h
AN: S23A-0299    [Abstracts]
TI: Crustal stress evolution of last 700 years in North China and earthquake occurrences
AU: * Wan, Y
EM: wanyg217217@vip.sina.com
AF: College of Disaster Prevention Techniques, Yanjiao, Beijing, 101601 China
AU: Shen, Z
EM: zshen@ies.ac.cn
AF: Institute of Geology, CEA, P.O.Box 8703, Beijing, 100029 China
AU: Gan, W
AF: Institute of Geology, CEA, P.O.Box 8703, Beijing, 100029 China
AU: Li, T
AF: Institute of Geology, CEA, P.O.Box 8703, Beijing, 100029 China
AU: Zeng, Y
EM: zeng@seismo.unr.edu
AF: Seismological Lab, University of Nevada, Reno, NV 89577 United States
AB: We simulate the evolution process of cumulative Coulomb failure stress change ($\Delta$CFS) in North China since 1303, manifested by secular tectonic stress loading and occurrence of large earthquakes. Secular tectonic stress loading is averaged from crustal strain rates derived from GPS. Fault rupture parameters of historical earthquakes are estimated as follows: the earthquake rupture length and the amount of slip are derived based on their statistical relationships with the earthquake intensity distribution and magnitude, calibrated using parameters of instrumental measured contemporary earthquakes. The earthquake rake angle is derived based on geologically determined fault setting parameters and seismically estimated orientation of regional tectonic stresses. Assuming a layered visco-elastic medium, we calculate stress evolution resulted from secular tectonic loading and coseismic and postseismic deformation. 49 M­Y6.5 earthquakes occurred in North China since 1303. Statistics shows that 39 out of the 48 subsequent events were triggered by positive $\Delta$CFS, yielding a triggering rate of 81.3%. The triggering rate for M­Y5 earthquakes after the 1976 Tangshan earthquake is 82.1%. The triggering rate is up to 90% if corrections are made for some aftershocks which were wrongly identified as occurred in stress shadow zones because of errors in parameter estimates of historical earthquakes. Our study shows very high correlation between positive $\Delta$CFS and earthquake occurrences. Relatively high $\Delta$CFS in North China at present time is concentrated around the Bohai Sea, the west segment of the Northern Qinling fault, western end of the Zhangjiakou-Bohai seismic zone, and the Taiyuan basin in Shanxi rift zone, suggesting relatively higher earthquake potential in these areas.
DE: 7223 Seismic hazard assessment and prediction
DE: 7205 Continental crust (1242)
DE: 7209 Earthquake dynamics and mechanics
SC: Seismology [S]
MN: 2004 AGU Fall Meeting