US Earthquakes: East vs. West

Yesterday’s earthquake, with its epicenter just 90 miles south of our Reston, Virginia headquarters, shook our building with 30+ seconds of deep rumbling here at Nature’s Best Photography. There was no warning and the aftershocks may continue through the next weeks. The Smithsonian National Museum of Natural History in nearby DC is open today, but the Gem and Dinosaur Halls are closed for assessments. The world’s largest obelisk, the 127-year-old Washington Monument, will be closed indefinitely after a crack in the very top of the 555-foot-high stone spire was discovered. This map from the US Geological Survey, based here in Reston, shows the current information on earthquakes around the world. Learn more on their website.

Interesting to note:
US East coast quakes are different than the more frequent occurrences in the West.

To quote from the Huffington Post: (click here for the whole story)

WASHINGTON (Associated Press) — The East Coast doesn’t get earthquakes often but when they do strike, there’s a whole lot more shaking going on. The ground in the East is older, colder and more intact than the West Coast or the famous Pacific Ring of Fire. So East Coast quakes rattle an area up to 10 times larger than a similar-sized West Coast temblor.

“They tend to be more bang for the buck as far as shaking goes,” said Virginia Tech geology professor James Spotila.

Tuesday’s 5.8-magnitude quake was centered in Virginia and was felt up and down the Eastern seaboard for more than 1,000 miles. There hasn’t been a quake that large on the East Coast since 1944 in New York.

While this was a rarity for the East, a 5.8 quake isn’t unusual for California, Oregon, Washington and Alaska, where one occurs about once a year. Those states have had 103 quakes 5.8 or bigger since 1900, compared to now two in the East.

The ground is different in the East in a way that makes the shaking travel much further, allowing people to feel the quake several states and hundreds of miles away.

The rocks in the Earth’s crust in the East are colder, older and harder, which means seismic waves travel more efficiently and over greater distances. Rocks on the West Coast are relatively young and broken up by faults.

“An intact bell rings more loudly than a cracked bell and that’s essentially what the crust is on the East Coast,” USGS seismologist Lucy Jones told a news conference in Pasadena, Calif.

In the East, hurricanes are the worry far more than quakes. Former FEMA chief Witt said people on the West Coast know what to do in an earthquake: drop to the floor, cover their heads and hold on to something sturdy until the shaking stops.

Find out how the animals reacted on the National Zoo Website:
The Zoo has a flock of 64 flamingos. Just before the quake, the birds rushed about and grouped themselves together. They remained huddled during the quake.

NEXT UP: we are bracing for the effects of the first hurricane of the 2011 season. “Irene” is expected to hit US mainland later this week.

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