How do earthquakes get measured on the Richter and moment magnitude scales?

Seismographs record ground motion as seismic waves pass through Earth. The original Richter scale, developed in 1935 by Charles F. Richter and Beno Gutenberg, worked well for local California quakes but became less accurate for very large events. Today, scientists usually use moment magnitude, which is based on the size of the fault rupture, the amount of slip, and the rigidity of the rocks. Because the scale is logarithmic, each whole-number increase represents about 32 times more released energy. That means a magnitude 7 earthquake releases far more energy than a magnitude 6, even though the number looks only one step larger.