After Haiti and Chile, are earthquakes increasing in frequency?

The Miami HeraldMarch 1, 2010 

Two nations, two months, two massive, deadly earthquakes.

Are we heading into a period of increased seismic activity?

No reason to think so, say local experts. Earthquakes happen all the time, though not always in populated areas, meaning we don't really take note.

An earthquake as powerful as the one that devastated Haiti takes place somewhere on earth about once a month, said Tim Dixon, geophysics professor at the Rosenstiel School of Marine and Atmospheric Science in Miami.

The quakes in Haiti (7.0 on the Richter scale) and Chile (8.8) have no bearing on each other since they involve different fault lines.

This much is predictable: Chile can expect aftershocks "for weeks and months," said Dr. Grenville Draper, geologist at Florida International University. By late Saturday, more than 50 aftershocks of 6.0 or greater already had rattled Chile -- and a 6.3 had been felt in Salta Argentina, 675 miles northeast of Santiago, according to the United States Geological Survey.

"This was a big one," said Dixon. "A really big one."

How thunderous is an 8.8 quake? The energy released is between 500 and 900 times that of the magnitude-7.0 shaker that hit Haiti on Jan. 12, Dixon said. On the complex scale that measures earthquakes, an 8.0 quake releases 30 times the energy of a 7.0, and a 9.0 would release 30 times that, meaning 900 times more energy. An 8.8 would be somewhat less, Dixon said.

The amount of damage that earthquake energy causes depends on the soil in which they take place, how close they are to populated areas and whether buildings have been designed to withstand quakes.

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