The relationship between seismicity patterns and fracture zones beneath northeastern Japan

Analysis of microearthquake data shows that most of the high seismicity regions along the plate boundary correspond to the rupture areas of previous large interplate earthquakes and are bounded by the Landward extensions of the fracture zones in the Pacific plate, suggesting strong mechanical coupling between the Pacific plate and the overriding Eurosion plate. Focal mechanisms of intraplate earthquakes in and around the fracture zones far east off the Japan trench and that of intermediate-depth earthquakes beneath the landward extension of the fracture zones suggest continuation of the fracture zones through the subducted Pacific plate