The Richter scale is a measure of the strength of an earthquake. It was originally developed in 1935 by Charles F. Richter to measure the magnitude of earthquakes of moderate size (magnitude 3 to magnitude 7) by assigning a number that would allow the size of one earthquake to be compared with another. The scale was developed for temblors occurring in southern California that were recorded using the Wood-Anderson seismograph and whose epicenters were less than 600 km (373 miles) from the location of the seismograph. The Richter scale is logarithmic, meaning that each increase of one unit represents the release of about 31 times more energy than that represented by the previous whole number on the scale. However, for earthquakes measuring magnitude 6.5 or greater, Richter’s original methodology has been shown to be unreliable.

Today, earthquake magnitude measurement is based on the Moment Magnitude Scale (MMS). MMS measures the movement of rock along the fault and accurately measures larger earthquakes, which can last for minutes, affect a much larger area, and cause more damage. The Moment Magnitude can measure the local Richter magnitude (ML), body wave magnitude (Mb), surface wave magnitude (Ms).

In addition to the Richter scale and the Moment Magnitude Scale, there are also measures of earthquake shaking intensity, such as the Modified Mercalli Intensity Scale. The Mercalli scale measures the amount of shaking at a particular location and is based on the observations of the people who experienced the earthquake and the amount of damage that occurred.

To summarize, the Richter scale measures the strength of an earthquake, while the Moment Magnitude Scale measures the movement of rock along the fault. The Modified Mercalli Intensity Scale measures the amount of shaking at a particular location and is based on the observations of the people who experienced the earthquake and the amount of damage that occurred.