The seismic activity of faults is mainly assessed with respect to earthquake epicenters associated with the faults. Such assessments have been qualitative until the most recent time. To more precisely evaluate the seismic activity of faults, the authors [1] propose a quantitative index of seismic activity (QISA) of faults. The index provides for the assessment of changes in the fault activity within decades and even several years, i.e. within short periods of time that are considered instantaneous in the geological time scale. A number of faults in the Baikal rift system manifest quasiperiodical reactivation, as evidenced by the relevant QISA. However, QISAs do not take into consideration energy characteristics of the process and do not allow considering the geological and geophysical significance and possible consequences of the reactivation of specific faults.

Based on further researches in the given direction, a magnitude index of seismic activity (MISA) of faults is proposed. From the set of parameters which is similar to that used to assess QISA, its evaluation algorithm is designed. However, instead of the number of events which occurred in the area of dynamic influence of faults within the given time interval, the new algorithm considers recorded maximum magnitude of seismic events. For periods of several decades and years, the MISA quasiperiodical patterns are established for a number of faults.

In zones of dynamic influence of seismically active faults, monitoring seismic events by the proposed algorithms brings principally new ideas on complex short-period reactivation of faults and shows ways to a more precise assessment of the role of the periodic nature of fault reactivation that is significant for the middle- and short-term earthquake prediction.

The research was financially supported by the Russian Foundation for Basic Research (grants 04-05-64348, 05-05-64327) and Physical Bases and New Technologies of Middle-scale Earthquake Prediction (applied to seismically active zones in Siberia) Program.

References

Sherman, S.I., Sorokin, A.P., Savitsky, V.A. New methods of classification of seismically active faults by seismicity index // Doklady RAN, v. 401, 3, 2005. (In Russian)