What Is The Biggest Earthquake Ever?
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The biggest earthquake ever recorded was the 1960 Valdivia earthquake in Chile, which reached magnitude 9.5. It struck on May 22, 1960, killed an estimated 1,600-6,000 people in Chile and surrounding regions, and generated tsunamis that crossed the Pacific Ocean, causing additional deaths in Hawaii, Japan, and the Philippines.
Earthquakes have been recorded with modern instruments for over a century, but the very biggest stand out far above the rest. The 1960 Valdivia earthquake in Chile holds the record for the largest earthquake ever recorded at magnitude 9.5. The energy released was enormous and the consequences extended across the entire Pacific basin. Several other earthquakes have approached this magnitude in modern history, but none have exceeded it.
What was the 1960 Valdivia earthquake?
The 1960 Valdivia earthquake struck southern Chile on May 22, 1960 at magnitude 9.5, the largest ever recorded. According to Britannica's account of the 1960 Chile earthquake, the earthquake ruptured about 600 miles of fault along the boundary where the Nazca Plate sinks beneath the South American Plate. The shaking lasted approximately 10 minutes, with damaging effects across most of southern Chile. The earthquake killed an estimated 1,600-6,000 people, with the wide range reflecting uncertainty in counts from the chaotic aftermath. Coastal towns were devastated by both ground shaking and the immediate tsunami.
What are the other biggest earthquakes?
After the 1960 Chile earthquake at 9.5, the largest earthquakes ever recorded include: the 1964 Great Alaska earthquake at magnitude 9.2, the 2004 Indian Ocean earthquake at 9.1-9.3, the 2011 Tōhoku earthquake in Japan at 9.1, and the 1952 Kamchatka earthquake at 9.0. All of these were subduction zone earthquakes in the Pacific or related plate boundary regions. Magnitude 9+ earthquakes are extremely rare globally, occurring roughly once every 20-30 years on average. The 9.5 of 1960 stands at the top of the list and may approach the theoretical maximum for a single earthquake.
Why was this earthquake so large?
The 1960 Chile earthquake was so large because of the geological setting and the size of the fault that ruptured. Southern Chile sits along a major subduction zone where the dense Nazca Plate dives beneath the South American Plate. The fault interface here is enormous, extending hundreds of miles along the coast. The earthquake's massive size reflects the very large area of fault that slipped in a single event, generating an exceptionally large energy release. The slip averaged 20 meters over the entire rupture area, an unusually large displacement for a single earthquake.
Could a bigger earthquake happen?
Most seismologists believe magnitudes much above 9.5 are unlikely on Earth because of physical limits. The size of an earthquake depends on the area of fault that ruptures and how much it slips. Subduction zone faults can rupture across very large areas, but eventually they reach physical limits. Some calculations suggest the absolute theoretical maximum is around magnitude 9.7-9.8 for any plate boundary on Earth. Magnitude 10 or above would require an essentially complete rupture of the longest plate boundaries simultaneously, which has never been observed and seems physically implausible.
The biggest earthquake ever recorded was the 1960 Valdivia earthquake in Chile at magnitude 9.5. Several other magnitude 9+ earthquakes have occurred in subduction zones around the Pacific, including Alaska 1964, Sumatra 2004, and Japan 2011. Magnitudes much above 9.5 are unlikely on Earth due to physical limits on how much fault area can rupture in a single event.
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