Intraplate deformation in the Japanese Islands: a kinematic study of intraplate deformation at a convergent plate margin

Relative motions within the deforming Japanese Islands with respect to the Sea of Japan are determined using earthquake records over the last 414 years, slip rates on Quaternary faults, and angular change rates obtained from triangulation in the last century. The directions of the principal strain axes obtained from seismic, geological, and geodetic data are in general agreement with each other, with the minimum shortening axis oriented in a WNW direction. Intraplate deformation in southwestern Japan determined from the seismic data accommodates a velocity of 5.5±2 (1 σ) mm/yr in a direction parallel to the Nankai trough, which is about 25% of the plate motion velocity component parallel to the Nankai trough between the Philippine Sea and Eurasian plates. In northern Honshu, the velocity vectors from the seismic data are nearly parallel to the plate motion vector at the Japan trench, and the intraplate deformation accommodates about 6% of the total Pacific-Eurasian or North American plate motion velocity. -from Authors