Imaging of the crust using aftershocks of the 2000 western Tottori prefecture earthquake

On October 6, 2000, a large earthquake occurred in the western part of Tottori prefecture, Japan. To reveal the crustal structure in the fault area of this earthquake, we conducted aftershock observations using a multi-channel seismic array. Since natural earthquakes are not located on the surface of the earth, we developed a new method, the natural earthquake reflection profiling (NERP) method, to image the crust using natural earthquakes. We applied the NERP method to the aftershock data. The shallow area of the upper crust is reflective and the aftershock distribution is diffused three dimensionally in this area. Also found in this area are small less-reflective zones, in which brittle fracture does not occur and stable-slip deformation is dominant. It is possible that the stable-slip areas are distributed in the upper crust, which may contribute to the major characteristics of this earthquake.