Seismic Process in Active Faults of the Baikal Rift System

Well known is the role of faults as structural factors controlling ore and non-ore natural deposits and/or other geological formations, fluid permeability rates, certain magmatic phenomena and other geologically ancient and recent phenomena taking place on the Earth's surface. In terms of seismology, faults are considered as concentrators of stresses which generate seismic processes when discharged. The seismic processes take place within areas of dynamic influence of faults (ADIF). Since seismic events controlled by the fault occur at certain time intervals, it is common to use a notion of "tectonic (re-)activation" of the fault or its fragment. Due to considerably different durations of the geological development of large faults and instrumental measurements of seismicity, seismic process modeling is very challenging. However, attempts are undertaken to jointly consider a huge near-fault region of the long-term formation and seismic events that occur chaotically and almost instantaneously in terms of the geological time scale within the given region by analyzing (1) selective reactivation of faults within the real time scale, and (2) regularities of spatial and temporal migrations of seismic events within the limits of ADIFs. Introduced are two new notions: (1) a quantitative index of seismic intensity of a fault, i.e. a number of seismic events n of magnitudes M per a unit of the fault length L (km) for the given time interval t (years), the area of dynamic influence of the fault being given as m (km); (2) an area of dynamic influence of the fault, i.e. a space around the given fault axis wherein alterations of structural and geophysical fields are recorded. The Baikal rift system (BRS) being a well studied object with abundant data on fault tectonics and epicenter fields of earthquakes is taken as a sample to describe spatial and temporal regularities in fault reactivation within the real time scale. Regularities in the seismic process in the BRS are considered within the ADIFs. In a seismic zone, seismicity is predetermined by the behavior of an ensemble of seismically active faults varying in ranks; seismic events within the ADIFs occur in a quasi-oscillating migration pattern. An established regular pattern of the occurrence of seismic events is applicable for medium-scale earthquake prediction in any seismically active region of the world. The research was supported by the Russian Foundation for Basic Research, Grant 04-05-64348.