Magnitude and Energy of Earthquakes

Abstract

IN a paper presented at a meeting of the Seismological Society of America on April 29, 1955¹, we have revised previous work² on the relation of earthquake magnitude M to energy E (in ergs). Methods formerly used to extend the magnitude scale for local earthquakes to teleseisms lead to inconsistencies, so that in effect three different magnitude scales are in use: (1) M _L, the magnitude originally defined by Richter³ for local earthquakes in California as recorded on standard torsion seismometers. (2) M _S, that based on calculated ground amplitudes for surface waves of periods of about 20 sec. in shallow teleseisms. (3) M _B, that based on the amplitude/period ratio in body waves for both shallow and deep earthquakes.