Introduction to the 921 Earthquake: The 921 Earthquake, also known as the Chiji Earthquake, was a reverse fault-type earthquake that occurred in the mountains of central Taiwan at 1:47:15.9 a.m. on September 21, 1999 (local time). The magnitude was on the Richter scale. Magnitude 7.6, focal depth 8 kilometers. Severe shaking was felt throughout the island of Taiwan and lasted for 102 seconds. It was the deadliest natural disaster in Taiwan after the war.