Plate convergence and long-term crustal deformation in Central Japan

Surveys by continuous Global Positioning System in and around Japan reveale d that the Amurian Plate collides with the North American Plate in central Japan by similar to2 cm/yr. Long-term crustal deformation seems to be influ enced mainly by this collision although subduction of oceanic plates govern s short-term elastic deformation over the are. Here we study the long-term deformation field by carefully removing the short-term signals inferred fro m a-priori plate convergence vectors and coupling strengths predicted by a thermal model. The obtained field shows that the change in velocities occur s along the longitude 135 degrees similar to 137 degreesE, and there exist a relatively rigid block and zones accommodating strains. Characteristic co mpressional deformation is found northwest of Izu due possibly to the colli sion of the Izu-Bonin are with Honshu. Plate convergence rate along the Nan kai-Suruga Trough is considerably smaller in eastern parts, due partly to t he transition from the Amurian to the North American Plate of the landward side, and partly to the motion of the Izu microplate relative to the Philip pine Sea Plate. This accounts for longer recurrence intervals of interplate earthquakes in the Suruga Trough where the Tokai earthquake is anticipated to occur.