An analysis of the spatial distribution of geophysical filds in the source region of the 2013 Ilin-Tas (Aby) earthquake

Abstract

This article analyzes the powerful Ilin-Tas earthquake that occurred in the Chersky Range system in the territory of the Republic of Sakha (Yakutia) in 2013. The mountain system of the Chersky Range system is confied to the Chersky seismotectonic zone, which is part of the Arctic-Asian seismic belt separating the Eurasian and North American lithospheric plates in Northeast Asia. The earthquake magnitude at the epicenter was 9.0. Geophysical filds were used as a material to clarify the structural-tectonic features of the study area and their relationship with seismicity. Involving the data on spatial distribution of anomalies of magnetic and gravity filds made it possible to detail the parameters of the position of the Ilin-Tas fault, where the epicentre of the Ilin-Tas earthquake originated. This fault traces between the Indigirka and Kolyma rivers along the border of the junction of the Moma Range with the Indigiro-Zyryansk depression, and is traced by gradient transition zones from negative to positive values of ΔTa and Δg. The main seismic shock is confied to thickening of Δg isoanomalies, forming a gravitational step, within which gravity values decrease from south to north. The epicentral fild of this earthquake with aftershocks captures the western slope of the Andrey-Tas Range (northwestern flnk of the Moma Range). A qualitative analysis of the geophysical filds in the epicentral region of the earthquake is carried out. Materials of instrumental and macroseismic data, focal mechanism and seismotectonic setting of the focal zone are given in the article. The data obtained as a result of studying the Ilin-Tas earthquake consequences allows to reveal local seismic activity in details and specify seismodanger degree of north-east Yakutia.