A planet-shaking megathrust
On May 22, 1960, at 3:11 PM local time, the ground in southern Chile began to shake. It did not stop for approximately 10 minutes. This was the Great Chilean Earthquake, the most powerful seismic event ever instrumentally recorded. Registering 9.4–9.6 on the moment magnitude scale, its epicenter was located off the coast, with the city of Valdivia being the most affected. The event was a megathrust earthquake, the result of the Nazca Plate releasing immense stress as it subducts beneath the South American Plate.
The rupture zone was enormous, stretching for about 800 to 1,000 kilometers along the Chilean coast, from Arauco to the Chiloé Archipelago. The fault slipped an average of 11 meters, with some sections displacing as much as 30 meters. This immense movement of the seafloor caused extreme ground shaking and permanently altered the landscape. Large areas of the coast, including parts of Valdivia, subsided by up to 2 meters, turning dry land into new wetlands and estuaries overnight. Conversely, some areas, like Isla Guafo, experienced uplift of as much as 3 meters. The raw energy released was so great that it triggered Earth's free oscillations, vibrations of the entire world that were detectable by sensitive instruments for weeks after the main shock, a phenomenon never definitively observed before.
A Pacific-wide tsunami
Just 15 minutes after the shaking began, the first of several tsunami waves struck the Chilean coast. In some locations, the waves reached a staggering height of 25 meters (82 feet), completely destroying entire coastal villages like Puerto Saavedra. The tsunami did not stop at Chile's borders. Traveling at speeds comparable to a jet airliner, over 800 kilometers per hour (500 mph) in the open ocean, the waves radiated across the entire Pacific.
Approximately 15 hours after the earthquake, waves reaching 10.7 meters (35 feet) high slammed into Hilo, Hawaii, over 10,000 kilometers away, causing 61 deaths and massive destruction. About 22 hours after the quake, the tsunami reached Japan, where waves up to 5.5 meters high killed 138 people and destroyed over 1,600 homes. The Philippines also saw fatalities, with 32 people dead or missing. The disaster left an estimated two million people homeless in Chile and resulted in economic damages equivalent to over four billion dollars today. The total death toll from the earthquake and tsunami is estimated to be between 1,000 and 6,000 people globally.