Contents of 11.8 How are earthquakes measured?

11.8 How are earthquakes measured?

Diagram to show how movement is measured along of a fault in relationship to rock strength.

Fig 11.35

The moment-magnitude scale is based on the physical parameters of the earthquake event. The scale is similar to the Richter scale in that each number increase represents a 10x increase in seismic moment.

Note: while magnitude measures of either type represent changes of 10x, in actual energy, the difference between numbers is 32x. So a M7 has 100x more "seismic moment" than a M5 (10 x 10). However, the energy difference is 1024 (32 x 32).