HR: 1340h
AN: S43A-1064    [Abstracts]
TI: Relationship between dip angle and surface slip distribution
AU: * Kase, Y
EM: kasep@ni.aist.go.jp
AF: Active Fault Research Center, GSJ/AIST, AIST Tsukuba Central 7, Tsukuba, CA 305-8567 Japan
AB: We simulated spontaneous rupture processes on dipping faults under a triaxial compressional stress condition, using a 3-D finite-difference method. The distribution of rake angle on the earth surface depends on dip angle, and its mean value is not equal to direction of the maximum shear stress on the fault. This results imply that dip angle can be estimated using ratio of vertical slip to horizontal slip and dynamic rupture simulations. In our 3-D finite-difference model, we modeled fault dipping by mapping a parallelogram grid onto a rectangular grid (Inoue, 1996). The grid interval along the fault should be uniform for calculations of spontaneous rupture processes. A hypocenter is located on the center of the fault. Varying the dip angle, we calculate dynamic rupture processes under uniform or depth-dependent triaxial compressional stresses. When dip angle is steep, rake angle on the earth surface gently varies along strike, and its mean value is larger than the angle of the initial shear stress. On the other hand, rake angle is constant along most of strike and the mean value is consistent with the angle of the shear stress when dip angle is gentle. These can be explained by causes of vertical slip. In the steep fault, it is caused by strain resulted from a strike slip. In the gentle fault, however, vertical component of shear stress causes a vertical slip.
DE: 7200 SEISMOLOGY
DE: 7209 Earthquake dynamics (1242)
DE: 8010 Fractures and faults
SC: Seismology [S]
MN: Fall Meeting 2005