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.
Highlights
O Discrepancies arise among magnitudes as derived from local earthquake data (ML), body waves (MB) and surface waves (MS)
In attempting to refine the magnitude-energy relation it was found [Gutenberg and Richter 1956] that three imperfectly consistent magnitude scales had been in use: ML determined from records of local earthquakes according to the original definition [Richter 1935]; MS from the amplitudes of surface waves for shallow teleseisms, [Gutenberg and Richter 1936; Gutenberg 1945a]; mB from the amplitude/period ratio of body waves for teleseisms, shallow and deep-focus [Gutenberg 1945b, 1945c]
Magnitudes have been derived by the senior author, from surface waves and from body waves separately, for a selection of better recorded large shallow earthquakes as listed by Gutenberg and Richter [1954]
Summary
O Discrepancies arise among magnitudes as derived from local earthquake data (ML), body waves (MB) and surface waves (MS). In attempting to refine the magnitude-energy relation it was found [Gutenberg and Richter 1956] that three imperfectly consistent magnitude scales had been in use: ML determined from records of local earthquakes according to the original definition [Richter 1935]; MS from the amplitudes of surface waves for shallow teleseisms, [Gutenberg and Richter 1936; Gutenberg 1945a]; mB from the amplitude/period ratio of body waves for teleseisms, shallow and deep-focus [Gutenberg 1945b, 1945c].
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