Interplate coupling in the Tokai district, central Japan, deduced from continuous GPS data

I invert GPS displacement rates in the Tokai district to investigate strain accumulation associated with the anticipated Tokai earthquake. I apply a representation of interseismic strain accumulation at subduction zones by Savage [1983] and estimate a distribution of virtual normal fault slip (back-slip) on the plate boundary surface. Estimated back-slip fakes its maximum value of 30-40 mm/year under the Sea of Enshu. This value is nearly equal to the relative plate motion there, implying almost complete coupling. Backslip is smaller under Suruga Bay, and its direction is different from the relative motion between the Eurasian and the Philippine Sea plates. Localized deformation at the northern tip of the Philippine Sea plate may be responsible for this discrepancy, partitioning tectonic strain due to the plate convergence into faults on both sides of the Izu peninsula and also distributed strain inside the peninsula.