1960 Valdivia earthquake
|Date||22 May 1960|
|Countries or regions||Chile, Argentina, United States, Japan, Philippines|
|Casualties||2,230 – 6,000|
The 1960 Valdivia earthquake or Great Chilean Earthquake (Spanish: Terremoto de Valdivia/Gran terremoto de Chile) of Sunday, 22 May 1960 is to date the most powerful earthquake ever recorded, rating 9.5 on the moment magnitude scale. It occurred in the afternoon (19:11 GMT, 15:11 local time) and its resulting tsunami affected southern Chile, Hawaii, Japan, the Philippines, eastern New Zealand, southeast Australia, and the Aleutian Islands in Alaska.
The epicenter was near Lumaco (see map) some 570 kilometres (350 mi) south of Santiago, with Temuco being the closest large city, while Valdivia was the most affected city. The tremor caused localised tsunamis that severely battered the Chilean coast, with waves up to 25 metres (82 ft). The main tsunami raced across the Pacific Ocean and devastated Hilo, Hawaii. Waves as high as 10.7 metres (35 ft) were recorded 10,000 kilometres (6,200 mi) from the epicenter, and as far away as Japan and the Philippines.
The death toll and monetary losses arising from such a widespread disaster are not certain. Various estimates of the total number of fatalities from the earthquake and tsunamis have been published, with the USGS citing studies with figures of 2,231, 3,000, or 5,700 killed and another source uses an estimate of 6,000 dead. Different sources have estimated the monetary cost ranged from US$400 million to 800 million (or 2.9 to 5.8 billion in 2011 dollars, adjusted for inflation).
Earthquake development 
The 1960 Chilean earthquake was actually a series of strong earthquakes that affected Chile between 21 May and 6 June 1960. The first was the Concepción earthquake and the strongest was the Valdivia earthquake.
Concepción earthquakes 
The first Concepción earthquake was at 06:02 UTC-4 on 21 May 1960. Its epicenter was near Curanilahue. Telecommunications to southern Chile were cut off and President Jorge Alessandri cancelled the traditional ceremony of the Battle of Iquique memorial holiday to oversee the emergency assistance efforts. The second and third Concepción earthquakes occurred at 06:32 UTC-4 and 14:55 UTC-4, on 22 May.
Valdivia earthquake 
The Valdivia earthquake occurred at 15:11 UTC-4 on 22 May. This earthquake affected all of Chile between Talca and Chiloé Island, more than 400,000 square kilometres (150,000 sq mi). Coastal villages, such as Toltén, disappeared. At Corral, the main port of Valdivia, the water level rose 4 m (13 ft) before it began to recede. At 16:20 UTC-4, a wave of 8 m (26 ft) struck the Chilean coast, mainly between Concepción and Chiloé. Ten minutes later another wave measuring 10 m (33 ft) was reported.
Hundreds of people were already reported dead by the time the tsunami struck. One ship, Canelos, starting at the mouth of Valdivia River sank after being moved 1.5 km (0.93 mi) backward and forward in the river; its mast is still visible from the road to Niebla.
A number of Spanish-colonial fortifications were completely destroyed. Soil subsidence also destroyed buildings, deepened local rivers, and created wetlands in places like the Río Cruces and Chorocomayo, a new aquatic park north of the city. Extensive areas of the city were flooded. The electricity and water systems of Valdivia were totally destroyed. Witnesses reported underground water flowing up through the soil. Despite the heavy rains of 21 May, the city was without a water supply. The river turned brown with sediment from landslides and was full of floating debris, including entire houses. The lack of potable water became a serious problem in one of Chile's rainiest regions.
The earthquake did not strike all the territory with the same strength; measured with the Mercalli scale, tectonically depressed areas suffered heavier damage. The two most affected areas were Valdivia and Puerto Octay near the northwest corner Llanquihue Lake. The overall picture of damage showed that Puerto Octay was the center of a north-south elliptical area in the Central Valley where the intensity was at its highest if not counting the Valdivia Basin. East of Puerto Octay, in a hotel in Todos los Santos Lake, piles of plates were reported to have remained in place.
Two days after the earthquake Cordón Caulle, a volcanic vent close to Puyehue volcano, erupted. Other volcanoes may also have erupted, but none were recorded due to the lack of communication in Chile at the time. The relatively low death toll in Chile (estimated at 6,000) is explained in part by the low population density and by building practices that took into account the high geological activity of the region.
Tectonic interpretation 
The earthquake was a megathrust earthquake resulting from the release of mechanical stress between the subducting Nazca Plate and the South American Plate, on the Peru-Chile Trench. The focus was relatively shallow at 33 km (21 mi), considering that earthquakes in northern Chile and Argentina may reach depths of 70 km. Subduction zones are known to produce the strongest earthquakes on earth as their particular structure allows more stress to build up before energy is released. Geophysicists consider it a matter of time before this earthquake will be surpassed in magnitude by another. The earthquake's rupture zone was 800 km long, stretching from Arauco (37° S) to Chiloé Archipelago (43° S). The rupture velocity has been estimated as 3.5 km per second.
Natural disasters triggered 
The earthquake triggered numerous landslides, mainly in the steep glacial valleys of the southern Andes. Within the Andes most landslides occurred on forested mountain slopes around the Liquiñe-Ofqui Fault. Some of these areas remain sparsely vegetated while others have naturally developed more or less pure stands of Nothofagus dombeyi. These landslides did not cause many fatalities nor significant economical losses because most of the areas were uninhabited with only minor roads. One landslide did, however, cause destruction and alarm following its blockage of the outflow of Riñihue Lake. About 100 km (62 mi) south of Riñihue Lake landslides in the mountains around Golgol River caused this river to dam up and then burst creating a flood down to Puyehue Lake. The Golgol landslides destroyed also parts of the international Route 215-CH that connects to Bariloche in Argentina through Cardenal Antonio Samoré Pass.
Earthquake-induced tsunamis affected southern Chile, Hawaii, Japan, the Philippines, eastern New Zealand, southeast Australia and the Aleutian Islands. Some localised tsunamis severely battered the Chilean coast, with waves up to 25 m (82 ft). The main tsunami crossed the Pacific Ocean at a speed of several hundred km/h and devastated Hilo, Hawaii, killing 61 people. Hilo's position in the bay caused a cumulative bounce of tsunami waves far more destructive to Hilo than to other more exposed areas of Hawaii. In Japan, the tsunami arrived about 22 hours after the earthquake and 142 people were killed. Tsunami waves as high as 10.7 m (35 ft) were recorded 10,000 km (6,200 mi) from the epicentre, several as far away as Japan and the Philippines.
On 22 May, a tsunami occurred also in Nahuel Huapi Lake, on the Argentinean side of the Andes, more than 200 km away from Valdivia. The wave, most likely produced by an earthquake-triggered sediment slide at the lake bottom, killed two people and destroyed a pier in San Carlos de Bariloche city.
Riñihuazo flood 
During the Great Chilean Earthquake, several landslides west of Tralcán Mountain blocked the outflow of Rinihue Lake ( ). Riñihue Lake is the lowest of the Seven Lakes chain and receives a constant inflow from the Enco River. The blocked San Pedro River, which drains the lake, passes through several towns and the city of Valdivia before finally reaching Corral Bay.
Because the San Pedro River was blocked, the water level of Riñihue Lake started to rise quickly. Each meter the water level rose was equivalent to 20 million cubic meters, which meant that 4,800 million cubic meters of water would release into the San Pedro River (easily overpowering its flow capacity of 400 cubic metres (14,000 cu ft) per second if it rose above the final, 24-meter-high dam. This potential disaster would have violently flooded all the settlements along the course of the river in less than five hours, and had more dire consequences if the dam suddenly broke.
About 100,000 people lived in the affected zone. Plans were made to evacuate Valdivia, and many people left. To avoid the destruction of the city, several military units and hundreds of workers from ENDESA, CORFO, and MOP started an effort, called the Riñihuazo, to control the lake. Twenty-seven bulldozers were put into service, but they had severe difficulties moving in the mud near the dams, so dykes had to be constructed with shovels. The work was not restricted to the lake; drainages from other parts of the Seven Lakes were also dammed to minimize the flow into Riñihue Lake. These dams were removed later, with the exception of Calafquén Lake, which still retains its dam.
By 23 June, the main dam had been lowered from 24 to 15 m (79 to 49 ft), allowing 3,000 million cubic meters of water to leave the lake gradually, but still with considerable destructive power. The team was led by ENDESA engineer Raúl Sáez.
Cordón Caulle eruption 
On 24 May 38 hours after the main shock of the 1960 Valdivia earthquake, Cordón Caulle began a rhyodacitic fissure eruption. Being located between two sparsely populated and isolated Andean valleys, the eruption had few eyewitnesses and received little attention by local media, preoccupied with the huge damages and losses caused by the earthquake. The eruption fed a 5.5 km long and N135° trending fissure where 21 individual vents have been found. These vents produced an output of about 0.25 km3 DRE both in form of lava flows and tephra. The eruption ended on 22 July..
Consequences and response 
Urban impact in Valdivia 
It has been estimated that about 40% of the houses in Valdivia were destroyed, leaving 20,000 people homeless. The most affected structures were those built of concrete, which in some cases collapsed completely due to lack of earthquake engineering. Traditional wooden houses fared better and were in many places left uninhabitable but without collapse. Houses built upon tectonically elevated areas suffered considerably less damage compared to those on the lowlands. Many city blocks with destroyed buildings in the city center remained empty until the 1990s and 2000s, with some of them still used as parking lots. Before the earthquake, some of these blocks had modern concrete buildings built after the Great Valdivia fire of 1909. In terms of urban development Valdivia suffered the loss of the minor but significant Cau-Cau bridge, a bridge that has not been rebuilt. The other bridges suffered only minor damage. Land subsidence in Corral Bay improved navigability as shoal banks produced earlier by sediments from Madre de Dios and other nearby gold mines sunk and compacted. The earthquake destroyed Valdivia's flood barriers and general land subsidence exposed new areas to flooding.
In matters of foreign aid United States set up a field hospital following the earthquake. Aided by the United States a geological survey of Valdivia was done following the earthquake and resulted in the city's first geological map. Mexico built and donated the public school Escuela México in the aftermath of the earthquake.
The earthquakes are seen in retrospect as the culmination of a long period of economic decline that began with shifts in trade routes due to the expansion of railroads in southern Chile and the opening of the Panama Canal in 1911.
In 1974 Valdivia lost its capital status to Puerto Montt when the military government of Chile reorganized the country's administrative divisions. Valdivia had previously been a first level administrative center within Chile since the 16th century. It regained its status in 2007 with the creation of the Los Ríos Region.
Impact in the countryside 
The tsunami that struck the coast of southern Chile destroyed seaside farms killing both livestock and people. Barns and industrial structures were destroyed. The dairy industry was among the few industries of the affected zone that received investment after the earthquake. It received state support through a long-term policy after the earthquake. The earthquake also helped to establish a technological cooperation programme in the dairy sector. More specifically, the German and Danish governments helped to create the Centro Tecnológico de la Leche (lit. Technological Centre of the Milk) in the Southern University of Chile.
Creation of emergency committee 
After the 1960 Valdivia earthquake a committee was formed to solve problems caused by the earthquake. However this committee was not dissolved afterward and in 1974 it became ONEMI (Spanish acronym for National Emergency and Information Office) when it acquired by law independent status as a governmental office.
Human sacrifice 
In the coastal village Collileufu, native Lafkenches carried out a ritual human sacrifice during the days following the main earthquake. Collileufu, located in the Budi Lake area, south of Puerto Saavedra, was in 1960 highly isolated and inhabitants there spoke mainly Mapudungun. The community had gathered in Cerro La Mesa, while the lowlands were struck by successive tsunamis. Juana Namuncura Añen, a local machi, demanded the sacrifice of the grandson of Juan Painecur, a neighbor, in order to calm the earth and the ocean. The victim, 5-year-old José Luis Painecur, had his arms and legs severed by Juan Pañán and Juan José Painecur (the victim's grandfather), and was stuck into the sand of the beach like a stake. The waters of the Pacific Ocean then carried the body out to sea. The sacrifice came to be known after a boy in the commune of Nueva Imperial denounced to local leaders the theft of two horses that were allegedly eaten during the sacrifice ritual. The 2 men were charged with the crime of murder and confessed, but later recanted. They were released after 2 years. A judge ruled that those involved had "acted without free will, driven by an irresistible natural force of ancestral tradition." The story was mentioned in a Time magazine article, although with little detail.
Previous and later earthquakes 
There is evidence that a similar landslide and earthquake occurred in 1575. This earthquake was of similar strength and also caused a Riñihuazo. According to Mariño de Lobera, corregidor of Valdivia in 1575, a landslide blocked the outflow of the lagoon of Renigua and several months, in April, caused a flood. Mariño de Lobera states that while the flood killed many Indians, Spanish settlers waited on high ground until after the dam burst.
On 27 February 2010 at 03:34 local time an 8.8 magnitude earthquake occurred just to the north (off the coast of the Maule region of Chile, between Concepción and Santiago). This quake was reported to be centered approximately 22 miles (35 km) deep and several miles off shore. This 2010 Chile earthquake may be related or consequential to the 1960 tremor.
In popular culture 
A 1969 episode of the U.S. television series Hawaii Five-O titled "Forty Feet High and it Kills!" referenced the tsunami that devastated Hilo in 1960.
See also 
- 1964 Villarrica eruption
- List of earthquakes in Chile
- List of largest earthquakes by magnitude
- Seismicity of the Chilean coast
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|Wikimedia Commons has media related to: Great Chilean Earthquake|
- Chilean earthquake and tsunami — University of Washington
- Tsunami of 1960 — George Pararas-Carayannis
- Hawaii Events — Pacific Disaster Center
- May 22, 1960 South Central Chile Tsunami Amplitudes — National Oceanic and Atmospheric Administration