Honduras Earthquake

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Posting Date: May 28, 2009, 2:02:00 PM

A powerful 7.1 magnitude earthquake struck off the coast of Honduras early Thursday morning, killing at least five people and injuring more than 40 others. Officials expect the death toll to rise as reports continue to come in from the predominately poor villages and towns of the mountainous area along Honduras’s Caribbean coast closest to the quake’s epicenter. Homes and other buildings have been toppled in several locations, and damage has also been reported in neighboring Guatemala and other Central American countries. The earthquake briefly triggered a tsunami alert for much of Central America’s Caribbean coast. The earthquake hit at 3:24 a.m. local time (08:24 UTC) 39 miles (64 km) northeast of Roatan, the largest of Honduras's three Bay Islands, a popular tourist destination. It shook the area for more than 30 seconds; its focal depth was relatively shallow at 8.7 miles (14 km). Rescue officials said the quake knocked out power and caused minor damage to buildings on Roatan. Four of the five deaths so far reported were of children, aged 3 to 15, who died when their houses collapsed. Houses also collapsed in Puerto Cortes on the north coast of the country, and in Santa Barbara, further inland, where the ceiling of an old colonial church caved in. Fires broke out in the northern business city of San Pedro Sula, where workers were evacuated from factories that exhibited cracked walls. The city’s connection to the rest of the country, Democracy Bridge, which spans Honduras’s largest river, the Ulua, also collapsed. San Pedro Sula is the country’s second-largest city. The tremor took place along the Swan Fracture zone, a transform fault that separates the North American and Caribbean plates. The two plates slide past each other here at a rate of about 18mm per year. The Swan fracture zone extends from the Caribbean Sea westward into the land area of Central America in Southern Guatemala near the Guatemala-Honduras border. Thursday’s earthquake was the largest offshore quake to strike along the fracture zone since a 6.0 magnitude temblor hit there in 2002. The Caribbean-North America plate boundary fault is seismically very active. Most notably, on February 4th, 1976, a magnitude 7.6 quake struck about 180 miles west of the current earthquake, killing more than 17,000 people. A century earlier, in 1856, an earthquake of magnitude about 7.7 occurred in the same area as Thursday’s quake, probably rupturing the same segment or nearby segment of the Swan fracture zone. Earthquakes of similar magnitude also took place along two landward extensions of the Swan fracture zone in 1785, 1812, and 1921. Several countries in Central America have seismic codes modeled, in large part, on U.S. codes. Honduras, however, remains the only country in the region where there are no official seismic provisions for design codes. In the region generally, construction has been strongly influenced by historical connections with Spain and Britain. Masonry construction accounts for a major share of the building stock in the region. Perhaps 15% of total building stock is unreinforced masonry, which is among the construction types most vulnerable to ground shaking. In Honduras, about one quarter of all residential construction is estimated to be of adobe, about one third of wood, and over 40% to be of masonry. Much residential property, however, is uninsured. Commercial construction consists about equally of one third masonry and one third adobe, less than ten percent concrete and steel, and the remainder of wood. Earthquake take up rates in the region are generally low. Consequently, and because this event occurred well offshore, AIR expects insured losses will be minimal.

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Posting Date: May 28, 2009, 2:02:00 PM