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1960 Valdivia earthquake

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The 1960 Valdivia earthquake is the strongest earthquake ever recorded in history.

Graph of largest earthquakes 1906-2005
Graph of largest earthquakes 1906-2005

It occurred on May 22, 1960, in southern Chile. Most scientific studies place its magnitude between 9.4 and 9.6 on the moment magnitude scale. This massive event lasted for approximately ten minutes. The earthquake was a megathrust earthquake, which is a type of powerful tremor occurring at subduction zones. These zones are areas where one tectonic plate slides beneath another. This specific event released nearly a quarter of all global seismic energy recorded between 1906 and 2005.

1960 Valdivia earthquake
1960 Valdivia earthquake

To understand how this happened, we must look at the tectonic plates beneath the ocean. Chile sits along the Pacific Ring of Fire, a region known for high seismicity. The earthquake resulted from the release of mechanical stress between two plates. The Nazca plate was subducting, or sliding under, the South American plate at the Peru–Chile Trench. This movement caused a massive amount of energy to build up. The rupture zone was incredibly long, stretching from Arauco to the Chiloé Archipelago. The rupture velocity, or the speed at which the fault breaks, was about 2.5 kilometers per second.

Americas Tectonic Plate Map - by NOAA
Americas Tectonic Plate Map - by NOAA

Some scientists have a different theory about the exact mechanism. A 2019 research paper suggests the earthquake might have involved two different faults. This theory proposes a 9.07 strike-slip sub-event alongside a 9.37 main thrust sub-event. This would involve the Liquiñe-Ofqui fault moving at the same time as the main plate boundary. This idea helps explain how the earthquake seemed to "overspend" its tectonic budget. Usually, an earthquake releases a specific amount of stored slip deficit. This theory suggests two faults slipping nearly simultaneously allowed for such an enormous release of energy.

The disaster was actually a complex sequence of events rather than a single shock. It began with the Concepción earthquakes on May 21, 1960. The first was an 8.1 magnitude quake near Curanilahue. This was followed by two more large quakes on May 22, measuring 7.1 and 7.8 magnitude. These events formed a southward migrating foreshock sequence. The main Valdivia shock occurred only 15 minutes after the third foreshock. The entire sequence of intense activity lasted from May 21 until June 6, 1960.

The shaking caused immediate and devastating changes to the landscape. In Valdivia, soil subsidence caused the ground to sink in many areas. This created new wetlands, such as the Río Cruces and the Chorocomayo aquatic park. The earthquake also triggered numerous landslides in the steep glacial valleys of the Andes. These landslides occurred mostly on forested slopes near the Liquiñe-Ofqui Fault. While these landslides were massive, they caused few deaths because the areas were mostly uninhabited. However, one landslide blocked the outflow of Riñihue Lake, changing the local environment.

The earthquake also generated massive tsunamis that traveled across the Pacific Ocean.

These waves traveled at speeds of several hundred kilometers per hour. In Chile, localized tsunamis produced waves as high as 25 meters. The main tsunami traveled far beyond South America. It devastated Hilo, Hawaii, where waves reached heights of 10 meters and killed 61 people.

Hilo after Tsunami 1960
Hilo after Tsunami 1960

Other regions affected included Japan, the Philippines, New Zealand, and Australia.

Great Chilean Earthquake damage at Kamaishi
Great Chilean Earthquake damage at Kamaishi

Estimating the total impact of the disaster is difficult. The death toll is estimated to be between 1,000 and 6,000 people. The monetary cost was also massive, ranging from $400 million to $800 million. In Valdivia, the electricity and water systems were completely destroyed. Many ships were lost or wrecked due to the waves. For example, the ship Canelo was moved by the water and eventually wrecked in the river.

Sunken steamer Carlos Haverbeck and Canelos - Chile, in the autumn of 1960
Sunken steamer Carlos Haverbeck and Canelos - Chile, in the autumn of 1960

Even the local volcanoes reacted, as the Cordón Caulle vent erupted two days later.

Cordon Caulle eruption 1960
Cordon Caulle eruption 1960
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🖼️ Images & Media (10)
File:Americas Tectonic Plate Map - by NOAA.jpg
Americas Tectonic Plate Map - by NOAA.jpg
File:Graph of largest earthquakes 1906-2005.png
Graph of largest earthquakes 1906-2005.png
File:1960 Valdivia earthquake.jpg
1960 Valdivia earthquake.jpg
File:Tsunami travel time Valdivia 1960.jpg
Tsunami travel time Valdivia 1960.jpg
File:Sunken steamer Carlos Haverbeck and Canelos - Chile, in the autumn of 1960.png
Sunken steamer Carlos Haverbeck and...
File:Hilo after Tsunami 1960.jpg
Hilo after Tsunami 1960.jpg
File:Great Chilean Earthquake damage at Kamaishi.jpg
Great Chilean Earthquake damage at Kamaishi.jpg
File:Cordon Caulle eruption 1960.jpg
Cordon Caulle eruption 1960.jpg
File:The center of Corral was almost completely destroyed by a tsunami - Autumn 1960.png
The center of Corral was almost...
File:Destroyed steel factory near Corral - Photo from the autumn of 1960.png
Destroyed steel factory near Corral -...
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