How big was the Nicaragua earthquake of this morning?
A ‘quake which struck just off the coast of Nicaragua in the early hours of the morning on 2 March 2014 was initially assigned a magnitude of 6.5 (M6.5) by the United States Geological Survey, although the organisation later reduced this to M6.2.
Is this tremor, which occurred 160km from the capital, Managua, significant?
At the time of writing news media had not reported any damage or injuries and the Pacific Tsunami Warning Center has not issued a tsunami warning.
This appears to be another subduction zone quake, but the earth processes taking place to create these seismic events are fascinating.
Nicaragua Earthquake’s Tectonic Setting: Subduction and Earthquakes
Tectonic activity creates the continents and dictates their shape on the surface of our planet; such major processes inevitably have the power to generate major earth movements.
Central America is a classic case of seismic activity caused by major earth processes; it’s a narrow isthmus of land where tectonic forces are creating new land along the boundary between the Cocos plate to the west and the Caribbean plate to the east. The former (Cocos plate) is moving westwards against the latter (Caribbean plate), and is forced downwards (subducted) beneath the Caribbean plate at a rate of around 76mm per year along a deep ocean trench (the middle America Trench).
Although detailed information is as yet unavailable about the the 2 March event, the initial data give clue as to its causes. The depth (72km) in association with the location of the epicentre of the tremor (on the overriding plate around 120km east of the boundary) suggests that the focus of the earthquake was either at or close to the interface between the two plates. This leads to the conclusion that this event is a typical subduction zone earthquake.
Seismic History of Nicaragua
Like the rest of the area along the Middle America Trench, Nicaragua is prone to repeated middle- to high-magnitude earthquakes.
The country’s largest on record, an M7.6 in September 1992, killed 116 people; size is not always the key to the level of devastation.
The most devastating in terms of human life occurred in 1972, when an M6.2 tremor killed an estimated 5,000 people and devastated large areas of the capital, Managua.
Shaking (and poor construction) are not the only factors which can render these regular tremors deadly. Offshore tremors, at shallow depth and in excess of a certain magnitude, can trigger tsunamis and in 1992 the loss of life and accompanying extensive damage are largely attributable to a tsunami, which affected coastal communities.
Nicaragua occupies just a short area of this vulnerable coastline and earthquakes along the subduction zone have cost thousands of lives in El Salvador, Costa Rica, Guatemala and Panama. Although nothing can be done to prevent (or, at present, predict) earthquakes, authorities can improve building codes and employ alert systems to reduce the death and damage created by future seismic events.
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