Which scale is typically used to measure the magnitude of an earthquake?

Richter's scale is used to express the magnitude of an earthquake.
The Richter scale is used to measure the magnitude of earthquakes. It was devised in 1935 by American seismologist Charles Richter in collaboration with Beno Gutenberg.

The Richter scale provides a quantitative measure of the earthquake's size or energy release.

Hence, the correct option is the Richter scale.