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.
The United States Geological Survey reports this event as the “largest earthquake of the 20th Century.” Other earthquakes in recorded history may have been larger; however, this is the largest earthquake that has occurred since accurate estimates of magnitude became possible in the early 1900s.
The earthquake occurred beneath the Pacific Ocean off the coast of Chile. Ground motion from this earthquake destroyed or damaged thousands of buildings. The Chilean government estimated that about 2,000,000 people were left homeless. It was fortunate that the earthquake occurred in the middle of the afternoon and was preceded by a powerful foreshock. That foreshock frightened most people from their buildings, placing them outside when the main earthquake occurred.
Most of the damage and deaths were caused by a series of tsunamis that were generated by the earthquake. These waves swept over coastal areas moments after the earthquake occurred. They pushed buildings from their foundations and drowned many people.
There are many different casualty estimates for this earthquake, with a maximum of around 6000. Most of the casualties were caused by tsunamis in Chile and from ground motion. However, people as far away as the Philippines were killed by this event.
Source: geology.com