The Revision of Earthquake Epicentres, Focal Depths and Origin-Times using a High-Speed Computer

Abstract

A program for an automatic computer has been developed to revise rapidly, provisional foci and origin-times of normal and deep-focus earthquakes. For each earthquake, up to 300 equations of condition found from P, pP and PKP observations are solved by least squares to give a correction to the trial location. Special attention is given to the weighting of observations and factors affecting convergence. Features of the program are that the theoretical travel-time tables are stored in complete form, and after each iteration a list of stations with corresponding distances, azimuths, and residuals as well as the root-mean-square error is printed. Applications to a 1954 hydrogen bomb explosion and a number of earthquakes are described. The results suggest that the program may be useful to research organizations requiring either regular or special location of epicentres.