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Episodes 2020; 43(4): 947-959

Published online December 1, 2020

https://doi.org/10.18814/epiiugs/2020/020058

Copyright © International Union of Geological Sciences.

Methodical approach to isolation of seismic activity migration episodes of the northeastern Baikal rift system (Russia)

by Anna V. Novopashina* and Olga F. Lukhneva

Institute of the Earth’s Crust, Siberian Branch of RAS, Irkutsk, Lermontov Street 128, 664033 Irkutsk, Russia

Correspondence to:*E-mail: avn@crust.irk.ru, olgal@crust.irk.ru

Received: August 8, 2019; Revised: March 31, 2020; Accepted: March 31, 2020

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

The orientation of deformation process development during rifting controls the strike of the regional active faults, which determine the epicentral field structure features in the northeast part of the Baikal rift system (BRS), characterized by current high seismic activity. Rose charts were plotted for the number of faults of each strike range. For zones of epicenter concentrations, the polygons of seismic data projection were determined in accordance with the general strike of most of the active faults and their average length. Taking into account the anisotropy of the fracture network, the spatiotemporal analysis of the earthquake epicentral field was carried out using GIS technology. The seismic activity migration episodes as a result of crustal deformation are inherent to a non-stationary seismic process for the investigated area. Migrations, characterized by constant rate, are recurred in places of intense lithosphere fracturing and change the direction in potential M≥5 earthquake and swarms occurrence sites. Ordered sequences of energy clusters most likely propagate at a depth of the fluid-saturated layer beneath the thickened granite batholith where the heat accumulated warms up the fluid and apparently reduces the viscosity of seismoactive layer. The existence of thickened plastic lithospheric layer and viscosity reduction of brittle crustal layer are conditions probably conducive to migration of seismic activity.