The Earthquake of September 16, 2020 in the Kirov–Kazhim Aulacogen

Abstract

Abstract On September 16, 2020, an earthquake was registered in the Slobodskoi district of Kirov Oblast. The instrumental data were processed on the basis of seismograms from 11 stations with epicentral distances from 69 to 660 km that cover the azimuthal range of 1.4°–322.8°, GAP = 124°. The earthquake is classified as a tectonic one and has the following parameters: coordinates 58.755° N, 50.588° E; time in the source t 0 = 01:04:44 (UTC); depth h = 6 km; energy class, after T.G. Rautian, K P = 9.4; M L = 3.2, and M S = 2.4; the error ellipsis parameters are Az Major = 20°; R Minor = 4.5 km, R Major = 7.3 km. The event was not felt by residents of the nearby localities, probably due to the fact that the seismic event was of low magnitude and occurred at night. In terms of tectonics, the earthquake of September 16, 2020 was confined to the Kirov–Kazhim aulacogen, which is, in turn, is located within the Volga-Ural anteclise of the Russian plate of the East European platform (EEP). Historical earthquakes are known near the epicentral area of the event, as well as instrumental ones with M L = 2.6–3.4. The Verkhoshizhemskoe earthquake of 2000 with I = V and two earthquakes with I = VII (1939 Sysola and 1897 Vyatka events) with documented macroseismic manifestations are the remarkable major events in the study area. Earthquakes occur mainly at the sides of the aulacogen and are probably confined to the northeast-trending faults that control the most submerged central graben of the aulacogen. The occurrence of seismic events within the EEP indicates that it is a fairly mobile structure, especially in its marginal parts.