About Haiti

Q&A about Haiti earthquake

(cctv.com)
Updated: 2010-01-14 15:44

How rare was the Haiti earthquake?

The Caribbean isn't exactly a hot zone for earthquakes, but they're not unheard of in the region.

Tuesday's earthquake was one of the largest ever to hit the area — the last time an earthquake this strong struck Haiti was in the 18th century.

Haiti takes up about half of the island of Hispaniola, while the Dominican Republic lies on the other side. In 1946, an 8.0-magnitude earthquake shook Samana, in the Dominican Republic, causing about 100 fatalities. The recent quake will likely have a much greater casualty toll because it hit a more densely populated region.

Why was the Haiti earthquake so devastating?

While magnitude is important, it's the intensity that matters to those affected by a natural disaster.

"In general, earthquakes have different characteristics whether they are in the ocean or on land and depending on the geologic setting they are in," Bedwell told LiveScience. "A mountainous and rocky setting is more characteristic of not as much ground shaking, opposed to abundant sediments and not as rocky where there's a potential for higher ground shaking. Haiti would be a more sediment type, more severe ground shaking geologic setting."

Depth is also important, as the source of the Haiti quake was 6.2 miles (10 km) below the Earth's surface.

"The depth of this earthquake in Haiti was very shallow, meaning that the energy that was released is very close to the surface, which can also be another characteristic that causes some violent ground shaking," Bedwell said. "An earthquake that's very deep – that energy has a chance to go through the Earth's crust before reaching the Earth's surface and possibly not causing as much shaking of the ground."

Unofficial USGS reports suggest the shaking lasted anywhere from 35 seconds to up to a minute, Bedwell said. "That's a pretty long amount of time for the ground to be shaking."

All of these effects get magnified when the infrastructure is shoddy and not built to withstand shaking. "Unfortunately, Haiti has a rather poor economy and not a wonderful building style for earthquake resistance, so we would expect that we would see quite severe and widespread damage from this earthquake," Michael Blanpeid, associate coordinator for the USGS Earthquake Hazards Program, said in a podcast.

A potentially similar effect was seen when a 8.0 magnitude earthquake struck China's Sichuan province, taking tens of thousands of lives. Earthquake engineers speculated the adobe and masonry buildings and homes, many of which were probably not reinforced with steel as building codes dictate, added to the earthquake damage, especially in more rural areas.