Refinement of the Deep Structure and Tectonic Movement Kinematics in the Area of the 2001 Salsk Earthquake Based on New Geophysical Data

Abstract

The article presents the results of a comprehensive study of seismotectonic, geological-geophysical, geodynamic, and seismological data in the region of the Salsk earthquake of May 22, 2001, M = 4.7, in the low-seismic region of the junction of the Scythian Plate and the East European Platform are presented. The parameters of this earthquake source associated with a deep tectonic structure identified by the microseismic sounding method (MSM) are estimated based on seismological and macroseismic data. The MSM section through the region of the Salsk earthquake was obtained by a submeridional profile about 65 km long across the strike of the Manych deflection zone. It was established that the hypocenter of the 2001 Salsk earthquake was confined to the Salsk fault zone included in the system of the Manych faults. This fault is expressed in a section in the form of a narrow subvertical strip with low seismic wave velocities traced from the Earth’s surface to a depth of more than 40 km. Immediately in the area of the earthquake below a depth of 10 km, the recognized fault zone has a local expansion at the point of transition through the plane when the sedimentary cover contacts with the Proterozoic basement. The assessment of the hypocentral position and source mechanism solution (a gently dipping thrust of the northern side at an angle of 25°–33°) correlates well here with the depth and inclination of the surface of the Proterozoic basement, the elements of which are also traced in the MSM section.