surface-wave magnitude scale

seismology

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July 21, 2026

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The surface-wave magnitude scale, denoted as M_s, is a method used in seismology to measure the size of an earthquake. It is based on the logarithm of the maximum amplitude of surface waves with a 20-second period recorded by seismographs.1

This scale, along with others like the Richter scale (M_L) and body-wave magnitude (m_b), helps quantify earthquake size. However, these scales can experience "magnitude saturation," where larger earthquakes are inaccurately represented. The moment magnitude scale (M_W) was developed to provide a more accurate measure, especially for the largest and most destructive earthquakes, by considering the seismic moment (M₀), which relates to the total energy released. A unit increase in M_s corresponds to approximately a 32-fold increase in energy.23

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Richter scale
Modified Richter scales
…traveling within Earth) and the surface-wave magnitude scale (M_S, which calculates the magnitude of Love and Rayleigh waves traveling along Earth’s surface). Although both scales continued to make use of seismographs and peak wave amplitudes, they became relatively reliable ways to calculate the energy of all but the largest earthquakes.…
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…traveling within Earth) and the surface-wave magnitude scale (M_S, which calculates the magnitude of Love and Rayleigh waves traveling along Earth’s surface). Although both scales continued to make use of seismographs and peak wave amplitudes, they became relatively reliable ways to calculate the energy of all but the largest earthquakes.…
Read More