INTERSEISMIC HORIZONTAL DEFORMATION IN NORTHERN HONSHU AND ITS RELATIONSHIP WITH THE SUBDUCTION OF THE PACIFIC PLATE IN THE JAPAN TRENCH

We investigate the origin of the geodetically observed interseismic ho rizontal deformation in northern Honshu by comparing shear strain rate s, principal strain rates, and velocity fields determined from geodeti c data with those calculated from the elastic dislocation models invol ving interplate motion at the Japan trench. The agreement between the observed and predicted directions of the principal strain axes indicat es that the geodetic strain field in northern Honshu is primarily elas tic strain transmitted from the Japan trench. In order to match the st rain rate tensors and velocity magnitudes obtained from the geodetic d ata, the dislocation model requires that 35% to 60% of the NUVEL1-A Pa cific-North American plate motion is locked at the plate interface alo ng the Japan trench. The down-dip depth limit of the locked zone is in ferred to be 55 km, which is consistent with the seismic data in the J apan trench.