Earthquake on 12.12.2020 with Mw=4.8 in the focal zone of the strong Chernogorsky earthquake on 07.28.1976 with Mw=6.4 in the Eastern Caucasus
Abstract
Relevance. The article discusses a significant earthquake that occurred on 12.12.2020 at 21:29 GMT in the Chechen Republic with a magnitude of Mw = 4.8. The epicenter of this earthquake and subsequent aftershocks is located in the junction between the southern part of the Tersko-Caspian trough and the structures of the northern slopes of the Greater Caucasus This area is associated with the Chernogorsky earthquake sources occurrence zone, which has a maximum magnitude of 6.5 and is a seismic generating region in the Tersky-Sunzha area. Studying such earthquakes is essential for understanding ongoing tectonic processes and can provide valuable data for assessing seismic hazards in the Chechnya region and its surrounding areas. Aim. The purpose of this publication is a comprehensive analysis of the information received about the significant earthquake on 12.12.2020, including the parameters of the hypocenter, the aftershock process, the source mechanism, spectral parameters and macroseismic studies on the manifestation of the main shock and aftershocks. Methods. For the primary processing of digital records, a standard technique implemented in the software computing complex WSG was used. The hypo71 program with a given velocity model for the studied area was used to determine the parameters of earthquake hypocenters. To clarify the parameters of aftershocks, the “double differences” method was additionally applied. The mechanism of the earthquake origin was calculated based on the characteristics of the first arrivals of the primary waves. Spectral analysis was performed using the SEISAN software. The results were processed and analyzed, leading to the determination of the type of seismic source mechanism as “reverse fault”. Historical information was provided, as well as a comparison of seismic activity in Chernogorsky and another significant earthquake that occurred in 1976. Foreshock and aftershocks processes were studied using modern methods for processing seismic data. The geological and geophysical characteristics of the epicentral region were described. The mechanisms of the main shock source and individual aftershocks were compared. The values of the spectral density, seismic moment and moment magnitude of the earthquake were obtained. Based on macroseismic data collected about the earthquake, a map of equal-magnitude points and isoseisms was constructed.
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