Interplate seismogenic zones along the Kuril-Japan trench inferred from GPS data inversion

In the subduction zones around Japan, where four plates interact with one another, large earthquakes have occurred repeatedly. These interplate earthquakes are part of the process of tectonic stress accumulation and release that is driven by relative plate motion. Stress accumulation between earthquakes results from slip deficit (slip that is insufficient to fully accommodate plate movement). For the prediction of large earthquakes, it is therefore important to monitor the distribution of slip deficit on plate interfaces. Here we apply an inversion method based on Bayesian modelling (using direct and indirect prior information on the magnitude and distribution of fault slip) to horizontal and vertical velocities from global positioning system data. For the seismically calm period between 1996 and 2000, we obtain a precise distribution of slip-deficit rates on the interface between the North American and Pacific plates around Japan, which reveals a trench-parallel belt of slip deficit with six peaks in the depth range of 10-40 km. These peaks agree with the source regions of past large interplate earthquakes along the Kuril-Japan trench. We conclude that the slip-deficit zones identified with our method are potential source regions of large earthquakes. © 2009 Macmillan Publishers Limited.