1999 Jiji Earthquake

Date: September 21, 1999 • Location: Nantou, Taiwan, Province of China

A 7.7 Mw earthquake struck Jiji, Taiwan, killing 2,415 people, injuring more than 11,000 others and causing about NT$300 billion (US$10 billion) in damage across the island.

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 same mathematically even though they are considered the same. Similar to the local magnitude/Richter scale (ML) defined by Charles Francis Richter in 1935, it uses a logarithmic scale; small earthquakes have approximately the same magnitudes on both scales. Despite the difference, news media often use the term "Richter scale" when referring to the moment magnitude scale.