Subsurface structure and slip-locking pattern of the Median Tectonic Line: A key to understand crustal activities in southwest Japan

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Key factors which characterize crustal activities in southwest Japan are (1) plate locking distribution on the upper interface of the subducting Philippine Sea plate and (2) subsurface structure and slip-locking pattern of the Median Tectonic Line (MTL) inland. Since the MTL fault plane is inclined northward and characteristic seismic activity and anomalous deformation pattern had been recognized in the northern side of the MTL, we deployed high-sensitivity seismometers and GPS receivers there to supplement nation-wide monitoring network. The forearc block south of the MTL moves westward relative to the northern one and shear zone is formed north of the MTL by the locking on the shallower part of the MTL fault plane and the stationary slip on the deeper part.