Foreshocks and aftershocks of strong earthquakes in the light of catastrophe theory
Schmidt Institute of Physics of the Earth of the Russian Academy of Sciences, Bolshaya Gruzinskaya ul. 10, Moscow, 123995, Russian Federation
In this review, general ideas and specific results from catastrophe theory and the theory of critical phenomena are applied to the analysis of strong earthquakes. Aspects given particular attention are the sharp rise in the fluctuation level, the increased reactivity of dynamical systems in the near-threshold region, and other anomalous phenomena similar to the critical opalescence. In the lack of a sufficiently developed theory of earthquakes, this appears to be a valid approach to the analysis of observations. The study performed brought out some nontrivial properties of a strong-earthquake source that manifest themselves both before and after the main rock discontinuity forms at the mainshock. In the course of the analysis of the foreshocks and aftershocks, such concepts as the round-the-world seismic echo, the cumulative effect of converging surface waves, and global seismicity modulation by the Earth's free oscillations are introduced. Further research in this direction is likely to be interesting and promising.