The Propagation of the Longitudinal Waves Produced by the Long Beach Earthquake

Abstract

The Long Beach earthquake of March 11, 1933, is the first which has occurred within the present network (1) of stations associated with the Seismological Laboratory at Pasadena, to be recorded at a large number of observatories. Its epicenter has been found by the hyperbola method (1) at 33°25' north geocentric latitude (33°35 1/ 2' geographic latitude) and 117°58' west of Greenwich) within a very few km., and the time of origin at 1h 54m 088 Greenwich time. Times of arrival of longitudinal waves have been given in the reports of some stations. The U.S. Coast and Geodetic survey, in addition, kindly has furnished me the readings of most of the stations in the United States. In table 1 these times of arrival of the P_n-waves are given, together with the distances calculated by use of the geocentric latitudes (2) of the stations. In this table, besides, the travel times as given by H. JEFFREYS (3) and the differences, observed - calculated times of arrival, are to be found. The constant term which must be added to the travel times of JEFFREYS has been assumed to be 6 seconds, which means that the time 0' which corresponds to the travel time 0 of JEFFREYS' tables has been assumed at 1h 54m 14s. In figure 1 the differences have been plotted. They correspond within 1 or 2 seconds to the corrections given already by JEFFREYS (4).