The propagation velocity of seismic activity migrating along the directions of the geodynamic forces prevailing in the northeastern Baikal rift system, Russia

Abstract

The recent tectonic stress field in the northeastern Baikal rift system (BRS) corresponds to the crustal deformation field. The stress-strain state of the Earth’s crust determines the fault network geometry and spatiotemporal structure of the epicentral field characterized by many earthquake swarms and earthquake migrations in the study area. In order to study the seismic process dynamics in different directions of the crustal deformation, the spatiotemporal analysis of earthquake time series has been made over the 1964–2015 instrumental period. To determine the relationship between crustal stress and spatiotemporal features of the epicentral field the seismic data were projected along horizontal stress tensor axes σ3 and σ2, consistent with major directions of the crustal deformation, a strike of major rifting structures, and a general azimuth of active fault groups. The NE-SW direction along the intermediate horizontal stress axes and main faulted arears exhibits slow earthquake migrations up to 60 km long, propagating with a modal velocity of about 30 kilometers per year. The NW-SE direction along the principal horizontal stress axes, orthogonal to the main faulted areas, is characterized by shorter migration sequences of less duration, propagating with a higher velocity than sequences registered in the NE-SW. The difference between the migration dynamics in mutually orthogonal directions can be attributed to the fault network configuration and the differences in the deformation process.