Guobiao in the context of "Surface wave magnitude"

The surface wave magnitude (${\displaystyle M_{s}}$) scale is one of the magnitude scales used in seismology to describe the size of an earthquake. It is based on measurements of Rayleigh surface waves that travel along the uppermost layers of the Earth. This magnitude scale is related to the local magnitude scale proposed by Charles Francis Richter in 1935, with modifications from both Richter and Beno Gutenberg throughout the 1940s and 1950s. It is currently used in People's Republic of China as a national standard (GB 17740-1999) for categorising earthquakes.

Recorded magnitudes of earthquakes through the mid 20th century, commonly attributed to Richter, could be either ${\displaystyle M_{s}}$ or ${\displaystyle M_{L}}$.