The Chilean earthquake of May 22, 1960, known also as the 1960 Valdivia earthquake or Great Chilean earthquake, lasted about 10 minutes. However, it was preceded by a foreshock sequence that began on May 21. The aftershocks that followed lasted until Nov. 1 of that year. This nearly six-month-long seismic event resulted in approximately 10 earthquakes measuring greater than 7.0 magnitude.
The 1960 Valdivia earthquake was the most powerful earthquake of the 20th century, and it took place in a series of seismic events happening in 1960 in Chile. The first foreshock measured 7.9 Mw and occurred near Concepción on May 21 at 10:00 UTC. Two more foreshocks above 7.0 Mw occurred the next day. The main event, which was centered near Valdivia and measured 9.5 Mw, occurred on May 22 at 19:11 UTC. It caused tsunamis in Chile, the United States, Japan and the Philippines, and it also resulted in a volcanic eruption that began on May 24 and lasted several weeks.
The Valdivia earthquake was 500 miles long and occurred along the Peru-Chile Trench, which is the line along which the South American and Nazca Plates meet. It affected 150,000 square miles from Talca to Chiloé Island and the number of casualties is estimated to be from 2,230 to 6,000. An hour after the earthquake, the area affected was hit by a series of tsunamis. Tsunamis spread throughout the Pacific Ocean, affecting coastal areas as far away as Alaska and Australia.