Velocities and strain rates in the Baikal-Mongolia region from the GNSS data

Abstract

We carried out study crustal deformations in the Baikal-Mongolian area as a key Indo-Asian collision zone including kinematic, geodynamic, and active tectonic aspects. The GNSS measurement data over the last 29 years formed the basis for calculating vectors of horizontal tectonic movements at a qualitatively new level. Recent results show the southeastern movement of the Trans-Baikal sites at an average velocity of 2 mm yr⁻¹.

We calculated the most realistic velocity of the opening of the Baikal Rift are of 0.9 ± 0.1 mm year⁻¹. On the basic long-term measurements we are computed the parameters of the rotation pole of the Siberian block (φ.: 53.107°; λ.: −99.793°; Mg.: 0.249282° Myr⁻¹).

The maximum values of area extension rates are mainly confined to the central parts of the Baikal rift and the Tunka depression. The amplitudes of the relative deformation extension exceed 20 × 10^-9 yr⁻¹.

The strain rate analysis also provided an opportunity to distinguish three deformation domains – contraction-, extension- and transition-dominated. Narrow zones identified between the extension- and contraction-dominated deformation domains are confined to large seismic events therein. Transitional zones are found in the central Mongolia, Transbaikalia and Tuva, with dilatation rates ranging from −5 to 5 × 10^-9 yr⁻¹.

A sharp positive to negative dilatation transition boundary is associated with recent significant seismic events.