The spatial density of foreshocks

Abstract

Aftershocks follow a well-defined spatial decay pattern in the intermediate field. Here I investigate the same pattern for foreshocks. Foreshock linear density decays as r (1.5 perpendicular to 0.1) over distances r of 0.1-30 km for 15 minutes before magnitude 3-4 mainshocks. This trend is the same as that of the aftershocks within the error of the measurement. This consistency of spatial decay can be explained by the clustering inherent in earthquake interactions. No additional preparatory process beyond earthquake triggering is necessary to explain the spatial decay. Citation: Brodsky, E. E. (2011), The spatial density of foreshocks, Geophys. Res. Lett., 38, L10305, doi:10.1029/2011GL047253.