Quasilinear Chains of Earthquakes in Clusters of Seismic Events: The Baikal Rift System

The identification of numerous quasilinear chains of earthquakes in the epicenter field of seismicity in the Baikal region and a study of these chains showed that the chains may include, not only chains of "migrating" earthquakes, but also those arising in a random space-time distribution of earthquakes. The present statistical study of the distribution of interepicenter distances showed that "migrating" chains may be formed within clusters of seismic events, and the distribution has been investigated. We note that chains in earthquake clusters can be identified based on the distribution of time, as well as from the distribution of distances. We have found the formation of earthquake chains in the areas of the following clusters of earthquakes: the Busingol earthquakes of 1976 and 1991; the South Baikal, the Kyakhta, and the Kichera earthquakes in the Tompuda sequence, the Oldongsin and Charuoda clusters. We showed that the chains were formed during the occurrence of these clusters. The areas of concentrated chains of clustered seismicity are found to have a relationship of the positions and directivity of the chains to the strike of fault zones, to near-fault cracks, and to the orientation of nodal planes at earthquake foci.