Surface wave magnitude

The surface wave magnitude ( M s {displaystyle M_{s}} ) 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.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, M s {displaystyle M_{s}} , and one on body waves, M b {displaystyle M_{b}} .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 M s {displaystyle M_{s}} , using an equation similar to that used for M L {displaystyle M_{L}} . The surface wave magnitude ( M s {displaystyle M_{s}} ) 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 the 1950s by the same researchers who developed the local magnitude scale ML in order to improve resolution on larger earthquakes: Recorded magnitudes of earthquakes during that time, commonly attributed to Richter, could be either M s {displaystyle M_{s}} or M L {displaystyle M_{L}} . The formula to calculate surface wave magnitude is: where A is the maximum particle displacement in surface waves (vector sum of the two horizontal displacements) in μm, T is the corresponding period in s, Δ is the epicentral distance in °, and