A method for epicenter determination

Abstract

The proposed method corrects for inhomogeneity in the azimuthal distribution of stations, by fitting the residuals to a cosine function of the azimuth. Early arrivals are assigned greater weights than late arrivals. The weights are optimized experimentally by using data from large explosions. Instead of tabulated travel times, polynomial approximations are utilized; hence the new programs require considerably less computer time and storage. The Longshot is normal to the axis of the trench, and is larger than previously reported. This means that the Longshot source term cannot be adequately accounted for by temperature differences between the sinking plate and the sorrounding mantle.