The December 15, 2021 Mw=4.8 earthquake on South Baikal_

Abstract The article presents the results of a detailed analysis of data on the earthquake that occurred on December 15, 2021, within the Mishikha depression in the southern basin of Lake Baikal. Despite a moderate energy level, the earthquake was felt at large epicentral distances and caused a noticeable public response, and therefore can be considered as significant one for the South Baikal region. Based on the joint inversion of amplitude spectra of surface waves and P-wave first-motion polarities, earthquake source parameters were obtaining seismic moment (M0=1.6·1016 N·m), moment magnitude (Mw=4.8), focal depth (h=22 km), as well as a focal mechanism, characterized by rift-type movements and representing an almost pure normal fault. It is possible that the earthquake source is associated with a local fault in the central part of the Mishikha depression, which is not shown on modern maps of active tectonics. Macroseismic data on the earthquake was collected via an online questionnaire posted on the website of the Baikal Branch of the Geophysical Survey of the Russian Academy of Sciences. The maximum observed shaking intensity was V (MSK-64) in settlements on the southern coast of Lake Baikal at a distance of 19–23 km. The shaking intensity IV (MSK-64) was observed at a distance of up to 170 km. The obtained results are of interest in studies on assessing and refining the seismic hazard of the Southern Baikal region.