THE SEPTEMBER 21, 2020, Mw = 5.5, BYSTRAYA EARTHQUAKE IN THE SOUTHERN BAIKAL REGION: PRELIMINARY RESULTS OF INSTRUMENTAL AND MACROSEISMIC OBSERVATIONS
N.A. Gileva1, E.A. Kobeleva1, Ya.B. Radziminovich1, 2, V.I. Melnikova1, 2, V.V. Chechelnitsky1
1 Baikal Branch of Federal Research Center «Geophysical Survey of Russian Academy of Sciences», Irkutsk, Russia
2 Institute of the Earth’s Crust, Siberian Branch of the Russian Academy of Sciences, Irkutsk, Russia
Corresponding author: N.A. Gileva, e-mail: nagileva@crust.irk.ru
Abstract. We consider the September 21, 2020, Mw = 5.5 seismic event, which occurred at the eastern part of the Tunka system of rift basins and was followed by a relatively strong mb = 4.6 aftershock. The earthquake epicenter is localized within the Bystraya basin in the zone of prolonged seismic quiescence and, possibly, is confined to the Main Sayan fault zone. The hypocenter depth, according to the solution of the Baikal Branch of the Geophysical Survey of the Russian Academy of Sciences, estimated as h = 18 km. The focal mechanisms of the main shock and strong aftershock are characterized by almost pure strike-slip movements, which is in good agreement with modern ideas about the tectonics of the area. The maximum shaking intensity observed in the settlements closest to the epicenter is estimated at VI–VII on the MSK-64 scale. Shaking intensity of V and IV was observed in settlements at distances over 180 and 500 km, respectively. The considered earthquake made it possible to obtain new data on the dynamic parameters of ground motions. The maximum peak ground acceleration (PGA) of 187 cm/s2 was recorded at the Talaya seismic station, which is the highest value for the territory of the Southern Baikal region during the period of earthquakes digital registration.
Keywords: earthquake, focal mechanism, focal depth, macroseismic data, peak ground acceleration, accelerogram, Main Sayan fault.
About the authors
GILEVA Nadezhda Alekseevna – Baikal Branch of Federal Research Center «Geophysical Survey of Russian Academy of Sciences». Russia, 664033, Irkutsk, Lermontova st., 128. E-mail: nagileva@crust.irk.ru
KOBELEVA Elena Anatolievna – Baikal Branch of Federal Research Center «Geophysical Survey of Russian Academy of Sciences». Russia, 664033, Irkutsk, Lermontova st., 128. E-mail: ekobeleva@crust.irk.ru
RADZIMINOVICH Yan Borisovich –Baikal Branch of Federal Research Center «Geophysical Survey of Russian Academy of Sciences». Russia, 664033, Irkutsk, Lermontova st., 128; Institute of the Earth’s Crust, Siberian Branch of the Russian Academy of Sciences. Russia, 664033, Irkutsk, Lermontova st., 128. E-mail: ian@crust.irk.ru
MELNIKOVA Valentina Ivanovna –Baikal Branch of Federal Research Center «Geophysical Survey of Russian Academy of Sciences». Russia, 664033, Irkutsk, Lermontova st., 128; Institute of the Earth’s Crust, Siberian Branch of the Russian Academy of Sciences. Russia, 664033, Irkutsk, Lermontova st., 128. E-mail: vimel@crust.irk.ru
CHECHELNITSKY Vladimir Vasilievich – Baikal Branch of Federal Research Center «Geophysical Survey of Russian Academy of Sciences». Russia, 664033, Irkutsk, Lermontova st., 128. E-mail: nagileva@crust.irk.ru
Cite this article as: Gileva N.A., Kobeleva E.A., Radziminovich Ya.B., Melnikova V.I., Chechelnitsky V.V. The September 21, 2020, Mw = 5.5, Bystraya earthquake in the Southern Baikal region: Preliminary results of instrumental and macroseismic observations, Voprosy Inzhenernoi Seismologii (Problems of Engineering Seismology). 2020. V. 47, No. 4. P. 55–71 [in Russian]. https://doi.org/10.21455/VIS2020.4-4
English translation of the article will be published in Seismic Instruments, ISSN: 0747-9239 (Print) 1934-7871 (Online), https://link.springer.com/journal/11990