Neo-seismotectonic Evolution in the Far-eastern Eurasian Plate around the Korean Peninsula

The Korean Peninsula and its neighboring regions are intraplate regions that comprise the far-eastern Eurasia plate. These regions have experienced complex tectonic evolutions including continental collisions and a rifting. The ambient stress fields around the Korean Peninsula are induced from nearby plate boundaries against to the Pacific, Philippine Sea, and Indian plates. Historically dozens of devastating earthquakes with magnitudes greater than 6 occurred around the Korean Peninsula. Strike-slip faulting is typically expected in such intraplate regions. Unusual major thrustal earthquakes occur in the East Sea, and normal-faulting earthquakes in the Yellow Sea. We investigate the neo-seismotectonics from geological features, seismicity, fault-plane solutions and seismic tomography. The compressional-axis directions in the East Sea rapidly change from NE to SE in the East Sea. High seismicity of reverse-faulting events is observed in the marginal regions of the East Sea. The regions correspond to rigid continental margins associated with the paleo-rifting. We suggest that the current compressional stress field causes reverse activation of the paleo-normal faults in the East Sea. East-west directional normal-faulting earthquakes are observed in central Yellow Sea between the Shandong Peninsula and the central Korean Peninsula. The E-W directional zoning and striking suggest a N-S directional collision and post-collisional delamination. This normal-faulting region is interpreted to be the northern margin of collision belt and the eastern extent of the Dabie-Sulu belt in the Yellow Sea. The observation suggests that the Dabie-Sulu belt is connected to the Korean Peninsula crossing the Yellow Sea.