HR: 1330h
AN: S42D-0196    [PDF]
TI: 3-D Dynamic Rupture Simulation of the 1995 Kobe Earthquake with a heterogeneous initial stress field
AU: * Song, S
EM: seisgoo@pangea.stanford.edu
AU: Beroza, G C
EM: beroza@pangea.stanford.edu
AB: The 16 January 1995 Kobe earthquake (Mw 6.9) occurred near the city of Kobe in western Japan, causing tremendous damage. We investigate the dynamic rupture process of the Kobe earthquake by spontaneous rupture modeling of a 3-D dynamic shear crack that reproduces the slip distribution found from kinematic waveform inversion of strong motion data. We find that using the heterogeneous initial stress field obtained from the static stress drop distribution computed from the kinematic slip model superimposed on a uniform final stress field successfully generates a dynamic model with a slip and rupture time distribution consistent with the kinematic source inversion. Large surface rupture was generated from high local stress drop of up to 50 bars beneath Awaji Island. Relatively small or negative stress drop with a large slip weakening distance beneath the city of Kobe might explain the lack of surface rupture in this area. Ide and Takeo (1997) suggest depth dependent slip weakening distances on the order of 0.5 - 1 m by analyzing the joint behavior of stress and slip inferred from their kinematic waveform inversion although they recognized that these values probably represent an upper bound. Although there are strong tradeoffs between the slip weakening distance and the yield stress (Guatteri and Spudich, 2000), our dynamic analysis with assumption of uniform yield stress just above the maximum initial stress indicates that the slip weakening distance, especially near the nucleation area, should be smaller (with an upper bound of ~ 0.1 m) than the estimate of Ide and Takeo (1997) in order for rupture to propagate spontaneously.
DE: 7209 Earthquake dynamics and mechanics
SC: Seismology [S]
MN: 2003 Fall Meeting