Interplate coupling and deformation in the accretionary prism in the Southwest Japan Subduction Zone

Frictional coupling at the plate interface will control seismicity and tectonics in subduction zones. In this study temperature structure and deformation in the accretionary prism in the Southwest Japan subduction zone are simulated using a two-dimensional isoviscous corner flow model. Using surface heat flow data the average interplate frictional stress and the effective viscosity of the prism are estimated to be 2 similar to 30MPa and 10(20-21)Pa.s, respectively. The low stress value is probably due to high pore pressures caused by dehydration reactions in the subducting crust. Estimated temperature of the landward limit of the seismogenic zone is 350 similar to 500 degrees C; when the frictional stress is considered, the temperature becomes similar to 100 degrees C higher than that of the onset of plasticity of granitic rocks (350 degrees C). The brittle-plastic transition of gabbroic rocks might control the depth extent of the seismogenic zone in lower crustal depths. Flow velocity at the bottom of the prism is estimated to be similar to 0.01m/yr, indicating that similar to 25% of the conversion has been consumed by the deformation of the accretionary prism in this subduction zone.