DALLAS - Earthquakes around the world have been associated with intense geologic activity around the Pacific Ocean.

Among those were the 2004 quake in Indonesia that generated tidal waves that killed more than 10,000, the 2001 quake in Seattle that created intense destruction and the 1989 quake in San Francisco that led the city to rebuild for several years.

However, why was Haiti hit by such a strong and destructive earthquake? Disturbances in the earth's crust are common, and they're still happening in Haiti.

Every day there's an earthquake somewhere in the world. Earthquakes are caused when chunks of the earth's crust rub against each other, like plates.

There are two kinds of earthquakes. One is a subduction fault, which is when one plate slides under another. That's what happened in Indonesia.

A transform, or strike-slip fault, happens when two plates slide against each other. That's what happened in Haiti.

When it comes to natural disasters, the island of Haiti seems to have a bulls eye on it.

Scientist have known of Haiti's earthquake vulnerability. But, geology and human nature conspired against protecting against it.

Earthquake damage results from four factors.

[First is] the magnitude of the event, said Brian Stumpf, a professor at Southern Methodist University. The second is the depth of the event. How close is this to the surface? ... What is the local geology on which the buildings are built? And finally, what are the buildings themselves like?

The Haiti earthquake was close to the surface and relatively intense. It can take hundreds of years for stress to build up in the earth's crust before the energy is violently released.

So, why not take action to prevent their damage? The reason may be more psychological than physical. Massive earthquakes tend to occur every few hundred years - several human lifetimes.


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