Seismicity in the generalized vicinity of large earthquakes

Earthquake catalogs are used to construct a generalized space-time vicinity of large earthquakes and to investigate the seismicity behavior in such areas. We investigate the character of the inverse cascade (seismicity rate increasing toward the time of the main shock) and of the aftershocks, as well as the lower seismicity increase relevant to the larger vicinity of the main shock. It is shown that the inverse and aftershock cascades are accompanied by several anomalies indicating the development of a precursory strength decrease in this space-time volume; this consists in decreased apparent stresses, an increased relative contribution of low frequency oscillations into the earthquake spectrum, and an increased correlation (homogeneity) of stress and strain. We emphasize the special significance of anomalies that also characterize the physical nature of the ongoing process, in addition to the existence of a strength decrease. An example of such an anomaly is provided