Seismic activity and focal mechanisms are governed by the effective stress field that is a combined result of regional tectonic processes and local stress perturbation. This study investigates the regional variation in the stress field in the eastern continental margin of the Eurasian plate around the Korean Peninsula and Japanese islands using a damped stress inversion technique based on the focal mechanism solutions of regional earthquakes. The dominant compressional stress is directed ENE–WSW around the Korean Peninsula and eastern China, E–W at the central East Sea and northern and southern Japan, NW–SE at central Japan, and N–S around the northern Nankai trough. The dominant compression direction changes rapidly in the East Sea and Japanese islands, which may be due to the combined effects of tectonic loading in the subduction zones off the Japanese islands and the India-Eurasia plate boundary. The crustal stress fields around the subduction zones off the Japanese islands present characteristic depth-dependent orientations. The orientations of the largest horizontal stress components, σH, in the subduction zones are subparallel with the plate convergence directions at shallow depths. The σH orientations are observed to rotate clockwise with the depth owing to slab subduction and lithospheric deformation. The regional stress field around the Japanese islands was perturbed temporally by the 2011 M9.0 Tohoku-Oki megathrust earthquake. The regional stress field was recovered in a couple of years. The stress field and tectonic structures are mutually affected, causing stress field distortion and a localized mixture of earthquakes in different faulting types.
Bibliographical noteFunding Information:
We are grateful to Dr. Iswarya Samikannu and two anonymous reviewers for valuable review comments. This work was supported by the Korea Meteorological Administration Research and Development Program under Grant KMIPA 2015-7040 and by the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education ( NRF-2015R1D1A1A01060198 ). Support from the Basic Research and Development Project of the Korea Institute of Geoscience and Mineral Resources (KIGAM, Project code No. GP2016-014 ) funded by the Ministry of Science, ICT and Future Planning, Korea is also acknowledged.
All Science Journal Classification (ASJC) codes
- Earth-Surface Processes