HR: 0830h
AN: S41C-0094    [PDF]
TI: Spatial and scale-dependent friction parameter derived from earthquake rate changes after a stress step by the 1999, Chi-Chi, Taiwan, earthquake
AU: * Wang, W
EM: seiwhwg@eq.ccu.edu.tw
AF: Institute of Applied geophysics, National Chung Cheng University, 160, Shanshin, Minghsiung, Chiayi, 621 Taiwan
AU: Chang, S
EM: sph8801@eq.ccu.edu.tw
AF: Institude of Seismology, National Chung Cheng University, 160, Shanshin, Minghsiung, Chiayi, 621 Taiwan
AB: Dieterich­Ýs fomulation for earthquake clustering derived from stability analysis of a spring-slider system with slowness law suggests that earthquake rate changes can be used as a stress meter for near-surface deformation and a tool for evaluation of the probability for the future large earthquakes. While employing this theory, most studies implicitly assumed friction parameters are spatially and magnitude independent. This assumption, however, needs to be justified. We conduct genetic-algorithm inversion to simultaneously obtain the spatial variation of long-term stressing rate and friction parameter based on the earthquake rate changes before and after the 1999, Chi-Chi, Taiwan, earthquake. We found that the long-term stressing rate from this inversion agrees well with GPS observations. Our results also suggest that the rupture characteristics of the Chi-Chi earthquake may be attributed to the spatial variation in A$\sigma$ (rate constitutive parameter and normal stress). Moreover, we found that A$\sigma$ systematically decreases with earthquake magnitude, which implies that Dieterich­Ýs fomulation for earthquake clustering is implicitly magnitude-dependent. Since stress drop derived form seismic moment release does not strongly correlate with earthquake magnitude, the magnitude-dependent friction parameter derived from this method may reflect the friction behavior of characteristic asperities only instead of the entire rupture area.
DE: 7209 Earthquake dynamics and mechanics
DE: 7215 Earthquake parameters
DE: 7230 Seismicity and seismotectonics
SC: Seismology [S]
MN: 2003 Fall Meeting