Surface Wave Magnitude

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:

    All forms of beauty, like all possible phenomena, contain an element of the eternal and an element of the transitory—of the absolute and of the particular. Absolute and eternal beauty does not exist, or rather it is only an abstraction creamed from the general surface of different beauties. The particular element in each manifestation comes from the emotions: and just as we have our own particular emotions, so we have our own beauty.
    Charles Baudelaire (1821–1867)

    As the bird trims her to the gale,
    I trim myself to the storm of time,
    I man the rudder, reef the sail,
    Obey the voice at eve obeyed in prime:
    “Lowly faithful, banish fear,
    Right onward drive unharmed;
    The port, well worth the cruise, is near,
    And every wave is charmed.”
    Ralph Waldo Emerson (1803–1882)

    We quaff the cup of life with eager haste without draining it, instead of which it only overflows the brim—objects press around us, filling the mind with their magnitude and with the throng of desires that wait upon them, so that we have no room for the thoughts of death.
    William Hazlitt (1778–1830)