Seismicity under Conditions of the Self-Organization of the Baikal Rift System

摘要

Study of the seismic moments of earthquakes in the Baikal region (φ = 48°-60° N, λ = 96°-122° E) has shown that the stress field of the Baikal Rift Zone (BRZ) underwent substantial spatiotemporal variations . Maps of the relative stress-strain state of the Earth's crust in this region exhibit the extended zone of maximums of structural-stress inhomogeneities that are closely correlated with areas of volcanic activity . These zones are characterized by the development of an unstable (in space and time) stress-strain state and the appearance of anomalous points coinciding in space and time with the onset of the stress field transformation that is induced by rifting. The stress field in such points drastically changes and then spreads over the lithosphere as a wave front. Such behavior is typical of structure-attractors in self-organizing unstable thermo-dynamic systems. Such geophysical processes have been recorded in all three zones of maximums of structural-stress inhomogeneities. Therefore, the BRZ may be classified as an open spatiotemporal self-organizing system. A question naturally arises as to how the process of self-organization is reflected in the BRZ seismicity. The present communication shows that the modern spatiotemporal structuring of regional seismicity is largely caused by the self-organization of the Baikal Rift System. This process was mainly related to rifting and was composed of consecutive variable-rate cycles that began to evolve in local structures as a rearrangement of the stress field. The geodynamic rearrangements (reactivations) were accompanied by significant (significance level 10%) variations of group seismic events.