HR: 0800h
AN: S41A-0955    [Abstracts]
TI: Seismic Wave Radiation of Rupture in Branched Fault Modeling
AU: * Uchida, K
EM: uchida@geo.kyushu-u.ac.jp
AF: Department of Earth and Planetary Sciences, Kyushu University , 6-10-1 Hakozaki, Fukuoka, 812-8581 Japan
AU: Kame, N
EM: kame@geo.kyushu-u.ac.jp
AF: Department of Earth and Planetary Sciences, Kyushu University , 6-10-1 Hakozaki, Fukuoka, 812-8581 Japan
AB: We simulate dynamic mode II rupture that finally forms a branched fault trace, where our main interest lies in the resultant seismic wave radiation due to the dynamic branching process. For this purpose we adopt the elastodynamic boundary integral equation method, which enables us to work with non-planar fault geometry. We consider a medium under biaxial compressional load in which Coulomb friction acts on rupture surfaces and apply a critical shear stress criterion in determining the direction and the extension of rupture tips . In our simulation, dynamic branching first occurs due to local off-plane stressing around the fast propagating tips and each branch increases its bending angle. The growth of branch is then arrested because the stress to be released on such branch becomes negative under biaxial compression.In order to find phases associated with the dynamic branching process, we synthesize waveforms of the branching model and compare them with those radiated from a planar fault model whose growth is arrested without branching. When the observation point is very near the branching point, we can successfully identify a small distinct branching phase in the component for which no wave radiation is expected from the planar model. Otherwise we cannot find little effect of the dynamic branching process on the seismic wave radiation. This is because the moment release rate on the branching part of the fault is negligible compared with that on the entire fault.
DE: 7260 Theory and modeling
DE: 7200 SEISMOLOGY
DE: 7209 Earthquake dynamics and mechanics
DE: 7212 Earthquake ground motions and engineering
SC: Seismology [S]
MN: 2004 AGU Fall Meeting