2010 Chile earthquake

The 2010 Chile earthquake and tsunami (Spanish: Terremoto del 27F) occurred off the coast of central Chile on 27 February 2010, at 03:34:12 local time (06:34:12 UTC). It had a magnitude of 8.8 on the moment magnitude scale, with intense shaking lasting for about three minutes. It was felt strongly in six Chilean regions (from Valparaíso in the north to Araucanía in the south) that together make up about 80 percent of the country's population. According to the United States Geological Survey (USGS) the cities experiencing the strongest shaking—VIII (Severe) on the Mercalli intensity scale (MM)—were Concepción, Arauco, and Coronel. According to Chile's Seismological Service, Concepción experienced the strongest shaking at MM IX (Violent). The earthquake was felt in the capital Santiago at MM VII (Very strong) or MM VIII. Tremors were felt in many Argentine cities, including Buenos Aires, Córdoba, Mendoza, and La Rioja. Tremors were felt as far north as the city of Ica in southern Peru (approx. 2,400 km (1,500 mi) away). It is the largest earthquake to hit Chile since the 1960 Valdivia earthquake. A 2014 study contended that water pressure built up between the two plates had been the catalyst.

The earthquake triggered a tsunami which devastated several coastal towns in south-central Chile and damaged the port at Talcahuano. Tsunami warnings were issued in 53 countries, and the wave caused minor damage in the San Diego area of California and in the Tōhoku region of Japan, where damage to the fisheries business was estimated at ¥6.26 billion (US$66.7 million). The earthquake also generated a blackout that affected 93 percent of the Chilean population and which went on for several days in some locations. President Michelle Bachelet declared a "state of catastrophe" and sent military troops to take control of the most affected areas. According to official sources, 525 people lost their lives, 25 people went missing and about 9% of the population in the affected regions lost their homes.

On 10 March, Swiss Reinsurance Co. estimated that the Chilean quake would cost insurance companies between 4 and 7 billion dollars. The rival German-based Munich Re AG made the same estimate. The losses to the economy of Chile caused by the earthquake are estimated at US$15–30 billion.

According to the USGS, the epicenter of the earthquake was about 3 km (1.9 miles) off the coast of Pelluhue, a town in the Maule Region. This is about 6 km (3.7 miles) west of the village of Chovellén, 15 km (9.3 miles) southwest of the town of Pelluhue and at a point approximately 100 km (62 miles) away from the following four provincial capitals: Talca (to the north-east), Linares (to the east), Chillán (to the south-east) and Concepción (to the south). Chile's Seismological Service located the quake's epicenter at about 34 km (21 miles) off the coast of Ñuble Region in the Biobío Region. This is 60 km (37 miles) north of Concepción and 170 km (110 miles) south-west of Talca.

The earthquake took place along the boundary between the Nazca and South American tectonic plates at a location where they converge at a rate of 80 millimetres (3.1 in) a year.^{[citation needed]} This earthquake was characterized by a thrust-faulting focal mechanism, caused by the subduction of the Nazca plate beneath the South American Tectonic Plates. The end-regions of the rupture zone coincided with the Andean oroclines of Maipo (33° S) and Arauco (37° S). This has been interpreted as suggesting a link between upper plate (South American plate) structure and rupture length.

Chile has been at a convergent plate boundary that generates megathrust earthquakes since the Paleozoic era (500 million years ago). In historical times the Chilean coast has suffered many megathrust earthquakes along this plate boundary, including the strongest earthquake ever measured, the 1960 Valdivia earthquake. More recently, the boundary ruptured during the 2007 Tocopilla earthquake in northern Chile.^{[citation needed]}

The segment of the fault zone which ruptured in this earthquake was estimated to be over 700 km (430 mi) long with a displacement of almost 10 meters, or 120 years of accumulated plate movement. It lay immediately north of the 1,000 km (620 mi) segment which ruptured in the great earthquake of 1960. Preliminary measurements show that the entire South American plate moved abruptly westward during the quake. A research collaborative of Ohio State and other institutions have found, using GPS, that the earthquake shifted Santiago 28 cm (11 in) to the west-southwest and moved Concepción at least 3 metres (10 ft) to the west. The earthquake also shifted other parts of South America from the Falkland Islands to Fortaleza, Brazil. For example, it moved Argentina's capital of Buenos Aires about 2.5 cm (0.98 in) to the west. Several cities south of Cobquecura were also raised by up to 3 meters. The maximum recorded peak ground acceleration was at Concepcion, with a value of 0.65 g (6.38 m/s²).

The locality of Tirúa south of Concepción recorded a 180 cm (71 in) uplift relative to sea level as result of the earthquake. This is the highest known uplift of the coast resulting from the earthquake. This uplift made a large islet emerge at the mouth of Lebu River.