Scientists find odd twist in slow ‘earthquakes’: Tremor running backwards. Largest Earthquake Recorded - World's Biggest Earthquake. "The Great Chilean Earthquake" The World’s largest earthquake with an instrumentally documented magnitude occurred on May 22, 1960 near Valdivia, in southern Chile.
It was assigned a magnitude of 9.5 by the United States Geological Survey. It is referred to as the "Great Chilean Earthquake" and the "1960 Valdivia Earthquake". The United States Geological Survey reports this event as the "largest earthquake of the 20th Century".