Spatio-Temporal Patterns of the Development of Strong Seismic Activations (1999-2007) in the Northern Baikal Area

摘要

The development of strong seismic activations in the northern Baikal area in 1999-2007 is considered. Based on maps of earthquake epicenter density, it has been shown that each activation is a separate group of seismic shocks (a cluster), whose scale and spatio-temporal pattern depend strongly on the stress-strain state of the crust. Estimates of seismic-moment tensors for strong earthquakes within the clusters demonstrate that the most numerous groups of shocks form in the rift stress field. With moving away to the southeast from the conventional axis of the Baikal rift, this field changes under amplification of the compressional stresses in Transbaikalia. Simultaneously, we observe a decrease in the number of seismic events and in their energy level. Totally, the considered seismic activations prove the small-scale block structure of the crust in the northern Baikal area and reflect the main features of the modern geotectonic development of this area related to the adjacent morphostructural zone, where most of fragments are involved in rifting and the other are affected by the activation of positive-sign block movements. The obtained results should be taken into account in the assessment of the seismic hazard of the studied territory.