微小地震の震源の求め方について

Abstract

The Poisson's ratio was studied and estimated as 0.2435ｱ0.0015 in this district. Thenwe can determine the origin time by the method of least squares, on a graph showing therelation between P arrival time and S-P time. In this case, we used only selected seismo-grams of which time accuracy is within 0.1 sec for the first arrival of P wave. And wecan determine the hypocenters from travel time of P wave as we know the crustal structureobtained by Kurayoshi-Hanabusa explosions. The results were fairly satisfactory.Concerning the epicenter, about 95% of earthquakes were determined in the accuracy ofｱ1.0km, but the determination of focal depth was not so satisfactory. This is mainlydue to the distribution of the seismological network.