An earthquake, called terremoto (moving earth) in Spanish, is caused by the shifting of sections of the earth’s outer shell (tectonic plates). Asevere earthquake can release as much as 10,000 times the energy of the first atomic bomb. Major earthquakes are relatively rare in Costa Rica, although the country has very active underground faults. In fact, Costa Rica is second only to Guatemala in Central American seismic activity.

The Richter Scale: The scale that measures earthquakes is named after North American seismologist Charles F. Richter, who developed the magnitude numbering system in 1935. Each number of the scale represents a tenfold increase in the amplitude of ground movements as measured by a seismograph. An earthquake measuring 6.0 is 10 times as severe as one of 5.0.

Costa Rica’s worst earthquake in recent times occurred on April 22, 1991, when a 7.1 terremoto struck the Caribbean side of the country, causing severe damage to Limón and destroying rail and many road connections between there and San José.