LOCATION OF THE SOUTHERN BOUNDARY OF THE OKHOTSK PLATE BASED ON A SET OF SEISMIC CHARACTERISTICS

The study focuses on determining the position of the southern boundary of the Okhotsk Plate based on the analysis of seismicity distribution in the Hokkaido and Honshu regions as well as adjacent territories according to the Japan Meteorological Agency (JMA) data for a period of 1998–2022. The seismicity distribution data are compared with regional seismic tomography models and the distributions of the directions of principal seismotectonic deformation axes according to data on the focal mechanisms of strong (Mw > 4.7) earthquakes using the International Seismological Center (ISC) data for a period of 1976–2022 and other recent geological–geophysical characteristics, such as gravity field heterogeneities, crustal thickness, volcanic manifestations, etc. It is revealed that the southern boundary of the Okhotsk Plate actually passes along the southern tip of Hokkaido Island (through the Oshima Peninsula and Uchiura Bay) rather than along the Hidaka Ridge or through Honshu Island, as previously assumed by other authors.