Initiation of plate boundary slip in the Nankai Trough off the Muroto peninsula, southwest Japan

To investigate variations in physical properties accompanying the development of the décollement, we used a neural network analysis of seismic attributes derived from 3D seismic reflection data gathered in the Nankai Trough convergent margin off the Muroto peninsula of southwest Japan. This analysis resulted in a detailed map of the geological features along the décollement and revealed a drastic change in physical properties at the sole of the protothrust. Ocean Drilling Program (ODP) data suggest that the décollement physical property change coincides with the initiation of slip. Furthermore, changes in the structure of the accretionary prism and reorganization of the décollement geometry also attend the initiation of plate boundary slip.