Statistical analysis of recent fault-plane solutions of earthquakes

Abstract

Abstract The large number of fault-plane solutions at present available in the literature permit one to calculate several statistical averages that have an important bearing upon geotectonics. The present paper represents a continuation of earlier work in this direction: 101 new fault-plane solutions are listed and the ratio of pressure to tension, strike slip to dip slip, and the average slip angle have been calculated for nine earthquake areas. Some of the older results are thereby corroborated, viz., that the “normal” character of earthquakes is to represent strike-slip faulting, and that the central Asian regions constitute an exception to this rule. In addition, it is now possible to make a breakdown with regard to depth. In this, a peculiar situation is found at 0.03 R depth, where the slip angle reaches a maximum. If the relationship between shallow and deep earthquakes be considered for any one area, however, it turns out that they are on the whole of the same character. Thus, whatever it is that causes earthquakes, acts in a similar fashion at all depths in any one area, but differs from one area to another.