| Abstract: | The eastern margin of the Japan Sea has been under convergent tectonics since sometime after the Pliocene. The suture line is on the ocean-continent boundary between the Japan-Yamato Basins and the Tohoku (Northeast Japan) Arc. Incipient subduction, and obduction, of the oceanic and sub-oceanic crust are observed along the suture line with the occurrence of numerous N-S trending, fault-bounded ridges and troughs. Focal mechanism solutions of several compressional type earthquakes with magnitudes of M = 6.9 to 7.7 which have occurred along the zone are consistent with the observation of geological thrust faults. The convergent stresses in the Japan Sea may be due to India-Eurasia collision and its associated intra-plate or inter-microplate movements in East Asia. The eastward movement of the Amurian Plate causes Baikal extension along its western margin and the Japan Sea convergence along its eastern margin. |
