Charles Richter and Beno Gutenberg's Paper Roll and Pen

Charles 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 1979, quantified the size of earthquakes. Inspired by Kiyoo Wadati's 1928 paper on shallow and deep earthquakes, Richter first used the scale in 1935 after developing it in collaboration with Beno Gutenberg; both worked at California Institute of Technology. The quote "logarithmic plots are a device of the devil" is attributed to Richter.

Invention of the Richter Scale
At the time when Richter began a collaboration with Gutenberg, the only way to rate shocks was a scale developed in 1902 by the Italian priest and geologist Giuseppe Mercalli. The Mercalli scale classified earthquakes from 1 to 12, depending on how buildings and people responded to the tremor. A shock that set chandeliers swinging might rate as a 1 or 2 on this scale, while one that destroyed huge buildings and created panic in a crowded city might count as a 10. The obvious problem with the Mercalli scale was that it relied on subjective measures of how well a building had been constructed and how used to these sorts of crises the population was. The Mercalli scale also made it difficult to rate earthquakes that happened in remote, sparsely populated areas.

The scale developed by Richter and Gutenberg (which became known by Richter's name only) was instead an absolute measure of an earthquake's intensity. Richter used a seismograph – an instrument generally consisting of a constantly unwinding roll of paper, anchored to a fixed place, and a pendulum or magnet suspended with a marking device above the roll – to record actual earth motion during an earthquake. The scale takes into account the instrument's distance from the epicenter, or the point on the ground that is directly above the earthquake's origin. Richter chose to use the term "magnitude" to describe an earthquake's strength because of his early interest in astronomy; stargazers use the word to describe the brightness of stars. Gutenberg suggested that the scale be logarithmic, so that a quake of magnitude 7 would be ten times stronger than a 6, a hundred times stronger than a 5, and a thousand times stronger than a 4. (The 1989 Loma Prieta earthquake that shook San Francisco was magnitude 7.1.)

The Richter scale was published in 1935 and immediately became the standard measure of earthquake intensity. Richter did not seem concerned that Gutenberg's name was not included at first; but in later years, after Gutenberg was already dead, Richter began to insist that his colleague be recognized for expanding the scale to apply to earthquakes all over the globe, not just in southern California. Since 1935, several other magnitude scales have been developed. Depending on what data is available, different ones are used, but all are popularly known by Richter scale.

Richter Scale
The Richter magnitude scale (often shortened to Richter scale) was developed to assign a single number to quantify the energy released during an earthquake.

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, and corresponds to a 31.6 times larger release of energy.

Since the mid-20th century, the use of the Richter magnitude scale has largely been supplanted by the moment magnitude scale in many countries. However, the Richter scale is still widely used in Russia and other CIS countries. Also worth noting is that earthquake measurements under the moment magnitude scale in the United States—3.5 and up, on the MMS scale—are still usually erroneously referred to as being measured under the Richter scale in the general public, as well as the media, due to the familiarity with earthquakes being measured by the Richter scale instead of the MMS scale.