9.5 Magnitude - May 22, 1960 near Valdivia, Chile
"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." 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.
Local Damage from Ground Motion and Tsunamis
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. They range from a low of 490 to a high of "approximately 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.
The costs of the damage were estimated to have been between $400 and $800 million in 1960 dollars, which would be about $3 to $6 billion today, adjusted for inflation.
This is one of the few earthquakes that has killed large numbers of people at distant locations. Tsunamis generated by the earthquake traveled across the Pacific Ocean at a speed of over 200 miles per hour. Changes in sea level were noticed all around the Pacific Ocean basin.
Fifteen hours after the earthquake, a tsunami with a runup of 35 feet swept over coastal areas of Hawaii. Many shoreline facilities and buildings near coastal areas were destroyed. Near Hilo, Hawaii, 61 people were reported killed by the waves.
In California, many small boats were damaged as the waves swept through marinas. At Crescent City, a wave had a runup of about 5 feet and caused damage to shoreline structures and small boats.
Waves up to 18 feet high hit the island of Honshu, Japan about 22 hours after the earthquake. There it destroyed more than 1600 homes and left 185 people dead or missing. Another 32 people were killed in the Philippines about 24 hours after the earthquake. Damage also occurred on Easter Island and Samoa.
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