## Richter magnitude scale |

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Characteristics |

The so-called **Richter scale**^{[1]} – also **Richter magnitude** or **Richter magnitude scale**, more accurately but informally **Richter's magnitude scale** – for measuring the strength ("size") of earthquakes refers to the original "magnitude scale" developed by ^{[2]} This was later revised and renamed the **Local magnitude scale**, denoted as "ML" or "M_{L}". Because of various shortcomings of the ML scale most seismological authorities now use other scales, such as the _{w} ), to report earthquake magnitudes, but much of the news media still refers to these as "Richter" magnitudes. All magnitude scales retain the

Prior to the development of the magnitude scale, the only measure of an earthquake's strength or "size" was a subjective assessment of the intensity of shaking observed near the ^{[3]} In the 1920s **Wood–Anderson Seismograph**, one of the first practical instruments for recording seismic waves.

In 1931 ^{[7]} Richter resolved some difficulties with this method^{[8]} and then, using data collected by his colleague ^{[9]}

To produce a practical method of assigning an absolute measure of magnitude required additional developments. First, to span the wide range of possible values, Richter adopted Gutenberg's suggestion of a ^{[10]} Second, he wanted a magnitude of zero to be around the limit of human perceptibility.^{[11]} Third, he specified the Wood–Anderson seismograph as the standard instrument for producing seismograms. Magnitude was then defined as "the logarithm of the maximum trace amplitude, expressed in ^{[12]} Finally, Richter calculated a table of distance corrections,^{[13]} in that for distances less than 200 kilometers^{[14]} the attenuation is strongly affected by the structure and properties of the regional geology.^{[15]}

When Richter presented the resulting scale in 1935, he called it (at the suggestion of Harry Wood) simply a "magnitude" scale.^{[16]} "Richter magnitude" appears to have originated when Perry Byerly told the press that the scale was Richter's and "should be referred to as such."^{[17]} In 1956, Gutenberg and Richter, while still referring to "magnitude scale", labelled it "local magnitude", with the symbol M_{L} , to distinguish it from two other scales they had developed, the _{S}) and _{B}) scales.^{[18]}