High Pore Fluid Pressure May Cause Silent Slip in the Nankai Trough

Abstract

Silent-slip events have been detected at several subduction zones, but the cause of these events is unknown. Using seismic imaging, we detected a cause of the Tokai silent slip, which occurred at a presumed fault zone of a great earthquake. The seismic image that we obtained shows a zone of high pore fluid pressure in the subducted oceanic crust located down-dip of a subducted ridge. We propose that these structures effectivelyextend a region of conditionallystable slips and consequently generate the silent slip.