Three-dimensional distributions of S wave reflectors in the source region of the 2000 Western Tottori Earthquake

We conducted a reflection analysis of the aftershock waveforms in the source region of the 2000 Western Tottori Earthquake. We obtained three-dimensional distributions of S wave reflectors in the source region by using similar to 9000 waveform traces. In the cross-section projected along the mainshock fault plane, we found three major reflection zones at depths of 15 - 25 km, 30 - 40 km and 50 - 60 km. The first and second are thought to correspond to the Conrad and the Moho discontinuities. The depth of these reflective zones seems to change along the fault direction. Also, cross-sections perpendicular to the fault plane show that the strengths of the reflected waves are different between the two sides of the fault plane. This result suggests that the mainshock fault plane is located at the boundary of medium properties and its near-vertical downward extension in the lower crust.