Magnitude and Energy of Earthquakes

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) ML, the magnitude originally defined by Richter3 for local earthquakes in California as recorded on standard torsion seismometers. (2) MS, that based on calculated ground amplitudes for surface waves of periods of about 20 sec. in shallow teleseisms. (3) MB, that based on the amplitude/period ratio in body waves for both shallow and deep earthquakes.