Statistics of apparent stresses in relation to the origin of an earthquakesource

Statistical patterns of apparent stresses are studied based on the analysis of the Harvard catalog of earthquakes and data from [Earthquakes in the US SR, 1988-1997]. It is shown that variations in characteristic stress values (averages and the median) provide constraints on the geodynamic situation and fluid regime in the Earth's crust and subduction zones. The scatter in stress values is modeled by a hierarchical cascade, which gives rise to a m ultifractal distribution of effective strengths in fault motion zones. The model proposed shows that the stresses tend to increase with the size of th e source. The results obtained are interpreted within the framework of a fl uid-metamorphic model of seismogenesis.