The Structure of Seismicity Field in the Baikal Rift Zone

A joint analysis of seismicity in the Baikal Rift Zone (BRZ) is carried out using modern instrumental data (Baikal Branch of the Federal Research Center "Geophysical Survey of the Russian Academy of Sciences," 1963-2021) combined together with historical and paleoseismological data on earthquakes. The structure of the seismicity field within BRZ is studied by the new statistical methods. The spatial resolution in the seismically active areas attained 100-120 km. The analysis revealed patches of seismic activity alternating with areas of relative seismic quiescence (seismic gaps). The seismic patches form a hierarchical structure. At the highest level (a spatial scale of 500-1800 km and a lifetime of 300 years and longer), three main patches of seismicity are identified within BRZ, defining the Sayan, Baikal, and Severomuiskii (North Muya) subregions. Smaller patches form a structure with a spatial scale of 100-500 km and a lifetime of 50-200 years. The patches of seismic activity reflect the segmentation of active faults during the seismotectonic evolution of the Earth crust. The estimates of the maximum regional magnitude M-max from instrumental data for 1963-2021 and from seismogeological data are compared. It is shown that quantile estimates Q(q) (T) of the maximum earthquakes in the future time interval T are preferable to the M-max estimates for the seismic risk problems.