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Published April 1969 | Published
Journal Article Open

Excitation of mantle Love waves and definition of mantle wave magnitude


A study is made of the excitation of mantle Love waves of 100 seconds period as a function of magnitude. 153 measurements of Love wave spectral density for earthquakes since 1930 ranging in magnitude from 6.0 to 8.9 are used to determine an excitation curve. The observations were first corrected to a standard distance of 90°. The excitation curve supports earlier results for mantle Rayleigh waves and, for strike-slip motion, an earlier curve for seismic moment versus mantle-wave magnitude. For dip-slip motion, the moments should be multiplied by a factor of about 2 1/2. A definition of mantle wave magnitude M_M, is set up, and the largest earthquake since 1930 found on this scale is the Alaskan earthquake of March 28, 1964 where M_M = 8.9. Other comparably large earthquakes, M_M = 8.8, were the Kamchatka earthquake of November 4, 1952 and the Chilean earthquake of May 22, 1960. It is suggested that mantle-wave magnitudes be used as a diagnostic aid in estimating the Tsunami potential of earthquakes.

Additional Information

Copyright © 1969, by the Seismological Society of America. Manuscript received September 16, 1968. The authors are indebted to Professor Charles F. Richter for critically reading the manuscript and offering constructive criticism. Thanks are due Mr. Ralph Gilman who provided records and calibration curves from the Pasadena (PAS) ULP instruments, and to the U. S. Coast and Geodetic Survey for supplying records. This research was supported by the National Science Foundation under Grant GA 1087 (Earthquake Mechanism).

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