High-resolution seismic reflection profiling across the Sone Hills fault zone, central Japan

Abstract

The Sone fault is a south dipping active reverse fault, trending WNW-ESE and bounding the southern end of the Kofu basin. This fault is located between the Kofu basin and Sone hills, and has displaced several river terraces. To reveal the subsurface geometry of the Sone fault, highresolution shallow seismic profiling was performed along the 2.8-km-long Makado and 0.8-km-long Ubaguchi seismic lines. On the Unagushi section, a south dipping fault surface is clearly recognized by the discontinuity between horizontal reflectors in the north and the domain showing a chaotic pattern of reflections. On the Makado section, the south dipping Sone fault is identified between the horizontal reflectors at the basin-side and dipping reflectors at the hill-side. On both seismic lines, the fault surface dips 30 degrees southward. The trace of The Sone fault is located along the present riverbed of R. Fuefuki, some hundred meters basin-ward shift from the trace estimated from tectonic geomorphology