A probability model for regional focal mechanism solutions

Abstract

This probability depends on A_ij (θ), the theoretical amplitudes from a particular orientation of the greatest and least axes of principal stress for the regional solution. Estimates of the principal stress axes T and P and their variances are computed by constructing a loss function based on the likelihood. The algorithm allows for the estimation of a mean regional solution and one for each event. A treatment of measures of fit and the winnowing of clusters of solutions is given. The resulting program has been applied to the determination of the regional solution and exceptional mechanisms for the main shock and 25 aftershocks of the great 1964 Alaskan earthquake and 19 small earthquakes in Bear Valley, California.