Two of the most common methods used to measure earthquakes are the Richter scale and the moment magnitude scale. The Mercalli scale also measures the effects of an earthquake at different locations.
The Richter scale calculates the strength of an earthquake based on measurements of the amplitude of the largest wave recorded on a seismometer as well as the distance between the earthquake and the same seismometer. It was developed to measure earthquakes in California.
The moment magnitude scale is the preferred scale because it covers a wider range of magnitudes and can be applied globally. The scale is based on the earthquake's moment release, a measurement that combines the distance a fault moved and the amount of force required to move it.