M 8.8 - 36 km WNW of Quirihue, Chile

Official Magnitude Reference:
Duputel, Z., Rivera, L., Kanamori, H., & Hayes, G. (2012).
W phase source inversion for moderate to large earthquakes (1990–2010).
Geophysical Journal International, 189(2), 1125-1147.

Tectonic Summary

The February 27, 2010, M 8.8 Chilean (Maule) earthquake occurred as the result of shallow thrust faulting generated at the gently sloping plate boundary fault that conveys the Nazca plate eastward and downward beneath the South America plate. At the location of the earthquake, the two plates are converging at a rate of 71 mm/yr. The fault rupture, largely offshore, exceeded 100 km in width and extended nearly 500 km parallel to the coast. The rupture began approximately 25 km deep beneath the coast and spread westward, northward, and southward. As the rupture spread, the fault slip (up to 15 m in magnitude) generated earthquake shaking and warped the ocean floor, triggering a tsunami along the fault-rupture area.

The written history of very large plate boundary earthquakes between Valparaiso and Concepción probably begins with an event near Concepción in 1562. Another earthquake 8 years later set off a tsunami that led Spaniards to rebuild Concepción on higher ground. A 1730 earthquake, which was probably centered near Valparaiso generated a tsunami that caused flooding and damage in Japan, as did the great Concepción earthquake of 1751. Charles Darwin and Robert FitzRoy observed the next major Concepción earthquake in 1835. The northern part of the 2010 rupture overlaps with the probable source area of the 1906 Valpariso earthquake of M 8.2. The tsunami associated with the 1906 earthquake produced damage in Hawaii, with reported run-up heights as great as 3.5 m.

Other parts of Chile’s coast have also produced notable earthquakes. South of Concepción, the source of the 2010 earthquake adjoins a fault rupture nearly 1,000 km long that produced the largest 20th-century earthquake worldwide, the giant earthquake of M 9.5 in 1960. An estimated 1,600 lives were lost because of the 1960 earthquake and tsunami in Chile, and the tsunami took another 200 lives in Japan, Hawaii, and the Philippines. At Valparaiso, a plate boundary earthquake of M 8.0 occurred in 1985. North of Valparaiso, a M 8.5 earthquake in 1922 generated a Pacific Ocean tsunami that reached heights of 9 m on the Chilean coast near Coquimbo and washed away boats in Hilo Harbor, Hawaii. Still farther north along the coast of Chile and Peru, great earthquakes with associated trans-Pacific tsunamis occurred in 1586, 1687, 1868, and 1877. Overall, along the Chilean coast, 13 earthquakes of M 7.0+ have occurred since 1973.

Since the beginning of the 20th century, M 8.2 earthquakes have occurred in 1906, 1943 and 1960, and a M 8.0 earthquake occurred in 1985, all in the vicinity of the February 27, 2010, earthquake. The M 8.2 earthquake in 1960 was a foreshock that occurred the day before the great M 9.5 Chilean earthquake.

Hayes et al. (2016) Tectonic summaries of magnitude 7 and greater earthquakes from 2000 to 2015, USGS Open-File Report 2016-1192. (5.2 MB PDF)