Reverse-faulting regime of stress implied from middle Miocene basaltic intrusions around the Cape Muroto, Southwest Japan

Abstract

Previous research has shown that stress conditions in the SW Japan arc changed from extension to compression during the middle Miocene. However, the compressional stress regime has not been clearly determined. To reconstruct the middle Miocene stress regime in the region, we analyzed basaltic intrusions in steeply northwest dipping units of the Shimanto accretionary complex around Cape Muroto. Analysis of orientation data for coherent units applying the Bingham distribution method and tilt correction indicates a compressive paleostress regime with a vertical σ3 axis, which is supported by orientation data collected from mélange units. This paleostress regime is consistent with buoyant subduction predicted from late Cenozoic plate reconstructions of SW Japan.