What's in a Name, Richter Scale

The Richter Magnitude Scale, often shortened to Richter scale, was developed to assign a single number to quantify the energy that is released during an earthquake. It was developed in 1935 by Charles Francis Richter in partnership with Beno Gutenberg, both from the California Institute of Technology. The scale was intended to be used only in a particular study area in California.

The scale is a base-10 logarithmic scale. The magnitude is defined as the logarithm of the ratio of the amplitude of waves measured by a seismograph to an arbitrary small amplitude. An earthquake that measures 5.0 on the Richter scale has a shaking amplitude 10 times larger than one that measures 4.0.

Since the 1970s, the use of the Richter scale has mostly been replaced by the Moment Magnitude Scale (MMS) in many countries. However, the Richter scale is still widely used in Russia and other European countries. The MMS was developed in the 1970s to succeed Richter magnitude scale. Even though the formulae are different, the new scale retains the continuum of magnitude values defined by the older one.

The MMS is now the scale used to estimate magnitudes for all modern large earthquakes by the US Geological Survey. Earthquake measurements under the Moment Magnitude Scale in the United States are still usually erroneously referred to as being quoted on the Richter scale by the general public and the media, due to their familiarity with the old Richter scale name vs. the newer MMS.