The primary scale historically used to measure the magnitude of earthquakes is the Richter scale , developed in 1935 by Charles Richter and Beno Gutenberg. It measures the magnitude based on the logarithm of the amplitude of seismic waves recorded by seismographs, specifically the largest wave amplitude
. Each whole number increase on the Richter scale represents a tenfold increase in wave amplitude and about 31.6 times more energy released by the earthquake
. However, the Richter scale has limitations, especially for very large earthquakes, and has largely been superseded by the Moment Magnitude Scale (Mw) , which provides a more accurate measure of large earthquakes by considering the physical size of the fault rupture and the amount of slip
. Despite this, the term "Richter scale" is still commonly used in media as a general reference to earthquake magnitude. In summary:
- Richter scale (Local Magnitude, ML): Measures amplitude of seismic waves logarithmically; widely known and historically important
- Moment Magnitude Scale (Mw): More accurate for large earthquakes; based on fault rupture size and slip
- Both scales use a logarithmic scale where each unit increase means roughly 31 times more energy release
Thus, earthquakes are measured using magnitude scales like the Richter scale and the Moment Magnitude scale, both logarithmic scales quantifying the size or energy release of an earthquake.
