A 7.7-magnitude earthquake strikes southern Pakistan, killing at least 327 people.

The moment magnitude scale is a measure of an earthquake's magnitude based on its seismic moment. Mw was defined in a 1979 paper by Thomas C. Hanks and Hiroo Kanamori. Before Hanks and Kanamori (1979), Kanamori (1977) developed Mw scale for large earthquakes above 7.5. Thus Mw and M are not the…