The surface wave magnitude (
) scale is one of the
magnitude scales used in
seismology
Seismology (; from Ancient Greek σεισμός (''seismós'') meaning "earthquake" and -λογία (''-logía'') meaning "study of") is the scientific study of earthquakes and the propagation of elastic waves through the Earth or through other ...
to describe the size of an
earthquake
An earthquake (also known as a quake, tremor or temblor) is the shaking of the surface of the Earth resulting from a sudden release of energy in the Earth's lithosphere that creates seismic waves. Earthquakes can range in intensity, from ...
. 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
Charles Francis Richter (; April 26, 1900 – September 30, 1985) was an American seismologist and physicist.
Richter is most famous as the creator of the Richter magnitude scale, which, until the development of the moment magnitude scale in 19 ...
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
China, officially the People's Republic of China (PRC), is a country in East Asia. It is the world's List of countries and dependencies by population, most populous country, with a Population of China, population exceeding 1.4 billion, sli ...
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
or
.
Definition
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