After huge Chile quake, big aftershocks

  @ibtimes on February 28 2010 7:30 AM

Chile's huge earthquake on Saturday morning was followed by big aftershocks.

The initial 8.8 magnitude quake at 3:34 a.m. local time hit about 200 miles southwest of Santiago, the nation's capital of 4.7 million people.

In the next five hours, another five aftershocks with a magnitude greater than 6 have hit the region, according to a compilation of data from the U.S. Geological Survey.

By early Sunday, data shows more than 100 aftershocks in Chile, greater than a magnitude of 5.

A magnitude 5.3 quake would be considered moderate while a 6.3 magnitude temblor would be considered strong. Quakes measuring more than 8.0 are considered great earthquakes.

The Chile quake released about 500 times more energy than the recent 7.0 magnitude quake in Haiti, yet the effects on the ground have been much different in terms of damage and lives lost due to better preparedness and building standards.

The magnitude of earthquakes, as measured by the Richter scale, measures the amount of seismic energy released on a mathematical basis. It does not measure intensity, which is non-mathematical and is based on the observed effects of ground shaking on people, buildings and natural features, according to the USGS.

Shortly after the initial quake at 3:52 a.m., a 6.2 magnitude aftershock shook the epicenter located in Maule region of Chile, just 70 miles from Concepcion, which has a population of 912,000.

Particularly jarring for Santiago residents was a 6.1 aftershock with an epicenter just 82 miles Northwest in the coastal city of Valparaiso. The largest was a 6.9 magnitude temblor about 300 miles south in the Bio-Bio region.

The USGS says each whole number step in the magnitude scale corresponds with the release of 31 times more energy than the amount associated with the preceding whole number value.

So-called microearthquakes are less than 2.0 in magnitude and are not commonly felt by people, just local measuring devices.

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