Abstract
The October 6,2000, M7.3 Tottori-ken-seibu earthquake involved a few surface fractures, which have been thought to be direct exposures of the source fault at the surface (surface fault trace) by several papers. However the fractures are unusually short (<1km) relative to the one estimated from the magnitude, and they are characterized discontinuity along the fault strike and split into two parallel-running breaks. Using freely slipping surface elements employing the boundary element method, I demonstrate that these fractures are more likely to be triggered slips to shed broadly distributed left-lateral shear stress produced by the subsurface fault. Even if the rupture of the source fault stopped at a depth of 1 - 4 km,0.5 km- to 1 km-length pre-existing weak surface fracture is calculated to have released 10 - 20 cm left-lateral slip, which amount is almost consistent with observed slip along the fractures. Thus, we cannot rule out the possibility that the fractures observed at the Tottori-ken-seibu earthquake were rather triggered slip.
