The surface wave magnitude () scale is one of the magnitude scales used in seismology to describe the size of an earthquake. It is based on measurements in Rayleigh surface waves that travel primarily along the uppermost layers of the earth. It is currently used in People's Republic of China as a national standard (GB 17740-1999) for categorising earthquakes.
Surface wave magnitude was initially developed in 1950s by the same researchers who developed the local magnitude scale ML in order to improve resolution on larger earthquakes:
The successful development of the local-magnitude scale encouraged Gutenberg and Richter to develop magnitude scales based on teleseismic observations of earthquakes. Two scales were developed, one based on surface waves, and one on body waves, mb.
Surface waves with a period near 20 s generally produce the largest amplitudes on a standard long-period seismograph, and so the amplitude of these waves is used to determine, using an equation similar to that used for .
— William L. Ellsworth, The San Andreas Fault System, California (USGS Professional Paper 1515), 1990-1991
Recorded magnitudes of earthquakes during that time, commonly attributed to Richter, could be either or .
Read more about Surface Wave Magnitude: Definition, Other Studies, See Also
Famous quotes containing the words surface, wave and/or magnitude:
“In the cold of Europe, under prudish northern fogs, except when slaughter is afoot, you only glimpse the crawling cruelty of your fellow men. But their rottenness rises to the surface as soon as they are tickled by the hideous fevers of the tropics.”
—Louis-Ferdinand Céline (1894–1961)
“The history of any nation follows an undulatory course. In the trough of the wave we find more or less complete anarchy; but the crest is not more or less complete Utopia, but only, at best, a tolerably humane, partially free and fairly just society that invariably carries within itself the seeds of its own decadence.”
—Aldous Huxley (1894–1963)
“Government is either organized benevolence or organized madness; its peculiar magnitude permits no shading.”
—John Updike (b. 1932)