| Abstrakt: |
A strong earthquake with a magnitude Mw = 7.0 occurred on February 13, 2020, at a depth of 142 km in the vicinity of the Southern Kuril Islands. Over recent decades, there has been an anomaly near the focal zone in the earthquake distribution over the layers of the double seismic focal zone in accordance with the seismic dislocation kinematic type compared to the other areas of the intermediate depths of the southern part of the Kuril arc. Inversion of the earthquake focal mechanisms of intermediate depth was performed for the southern part of the Kuril Islands along the upper and lower layers of the seismic focal zone. In the upper layer, compression prevails along the slab; the axis of maximum compression σ3 is mainly parallel to the slab and is oriented at an angle of 140–160° (320–340°) to the direction of its dip, i.e., subparallel to the Pacific Plate motion vector in the mantle in this area. The stress state of extension along the slab prevails in the lower layer; the axis of minimum compression σ1 is parallel to the slab and is mainly rotated by 20° (200°) clockwise from the direction of its dip. This orientation of the principal stress axes could indicate that, in addition to the slab unbending, their formation is affected by the mantle resistance to its movement. In the upper and lower layers, we marked the areas where the shear stress prevails that correspond to the kinematic type of transform faults, which are presumably seismically active on the descending plate. The most complex pattern of the stress state of the medium was obtained near the focus of the earthquake that occurred on February 13, 2020. Here, in the upper layer, an area with the stress state of extension and orientation of the principal axes corresponds more to the lower layer. Seismic quiescence is observed in the lower layer, near the focus of this earthquake within the area 60 km wide along the island arc and at the entire interval of intermediate depths. [ABSTRACT FROM AUTHOR] |
Full text from SpringerLink