The September 5th 2012 a magnitude 7.6 earthquake beneath the Nicoya Peninsula, Costa Rica, occurred as the result of thrust faulting on or near the subduction zone interface between the Cocos and Caribbean plates. At the latitude of this earthquake, the Cocos plate moves north-northeast with respect to the Caribbean plate at a velocity of approximately 77 mm/yr, and subducts beneath Central America at the Middle America Trench.
Over the past 40 years, the region within 250 km of the September 5th earthquake has experienced approximately 30 earthquakes with a magnitude 6 or greater; two of these were larger than a magnitude 7, and neither caused documented fatalities. The first was a magnitude 7.2 in August of 1978, 9 km to the north-northeast of the September 5th 2012 event; the second had a magnitude of 7.3, and struck a region just over 50 km to the east-southeast in March 1990. The closest earthquake to cause fatalities in recent history was the magnitude 6.5 April 1973 earthquake approximately 80 km to the northeast, which resulted in 26 fatalities and over 100 injuries.
Costa Rica's area (51,100 sq km/19,730 sq mi) is about the size of the states of Vermont and New Hampshire combined. It borders both the Caribbean Sea and the North Pacific Ocean, lying between Nicaragua and Panama. The Costa Rican terrain includes a rugged, central range of mountains that separate the eastern and western coastal plains. Its climate is mild in the central highlands, but tropical and subtropical in the coastal areas.
Unlike many of their Central American neighbors, present-day Costa Ricans are largely of European rather than mestizo descent. Descendants of 19th-century Jamaican immigrant workers constitute an English-speaking minority, about 3% of the population. Few of the native Indians survived European contact; the indigenous population today is less than 1% of the population.
Although explored by the Spanish early in the 16th century, initial attempts at colonizing Costa Rica proved unsuccessful due to a combination of factors, including: disease from mosquito-infested swamps, brutal heat, resistance by natives, and pirate raids. It was not until 1563 that a permanent settlement of Cartago was established in the cooler, fertile central highlands. The area remained a colony for some two and a half centuries. In 1821, Costa Rica became one of several Central American provinces that jointly declared their independence from Spain. Two years later it joined the United Provinces of Central America, but this federation disintegrated in 1838, at which time Costa Rica proclaimed its sovereignty and independence. Since the late 19th century, only two brief periods of violence have marred the country's democratic development. In 1949, Costa Rica dissolved its armed forces. Although it still maintains a large agricultural sector, Costa Rica has expanded its economy to include strong technology and tourism industries. The standard of living is relatively high and land ownership is widespread.
CIA World Factbook; U.S. State Department Background Notes; USGS Earthquake Hazards Program, 8/2012; 4/2012; 9/2012