Spatial distribution of earthquakes: the two-point correlation function

Abstract

The distribution of distances between pairs of earthquake epicentres and hypocentres has been determined for four local and two world-wide catalogues. These spatial correlation functions shows that the number of events per unit volume at distance R from any earthquake is proportional to R-α, where α is close to 1.0 for shallow earthquakes and increases to 1.5 or possibly larger for deeper events. This distribution of earthquakes is independent of magnitude and independent of the dimensions of the region under consideration. These results place limits on possible models of earthquake fault geometries.