Is the Big Apple an Earthquake Risk?

Being such a densely populated city, New York would not be a good place to be in the event of a large, or even medium sized, earthquake. Thankfully, New York is not one of the planet’s popular earthquake-hot spots. However according to research by a group of prominent seismologists, it is at more risk than people think.

The group, all based at Columbia University’s Lamont-Doherty Earth Observatory, believe that a pattern of small but nevertheless active faults in and around New York City increases the risk to the city.

There is a long history of small earthquakes in and around New York City. The authors have compiled a catalog totaling 383 earthquakes that have taken place between 1677 and 2007, occurring in a 15,000 square mile area around the city. One of the coauthors, John Armbruster, was charged with estimating sizes and locations of the quakes prior to 1930, when active recording began. He combed through newspapers and other records, attempting to decipher how big earthquakes were, and just when they happened.

What they found was three magnitude 5 earthquakes that occurred in 1737, 1783 and 1884; earthquakes that were strong enough to cause damage. And though there was little enough around for the first two to take much harm, the third earthquake toppled chimneys across the city and New Jersey. But here is the problem that was over a hundred years ago. "Today, with so many more buildings and people, a magnitude 5 centered below the city would be extremely attention-getting," said Armbruster. "We'd see billions in damage, with some brick buildings falling. People would probably be killed."

Another potential catastrophe waiting to happen lies in wait at the controversial Indian Point nuclear power plants, 24 miles north of New York City. The power plants sit across two previously undetected active seismic zones. This 25 mile fault is known as the Stamford-Peekskill line, running form Stamford, Conn., to the Hudson Valley town of Peekskill, N.Y., and passes within a mile north of the Indian Point location.

"Indian Point is situated at the intersection of the two most striking linear features marking the seismicity and also in the midst of a large population that is at risk in case of an accident," says the paper, published in the current issue of the Bulletin of the Seismological Society of America. "This is clearly one of the least favorable sites in our study area from an earthquake hazard and risk perspective."

"New York is not as prone to earthquakes as California and Japan, but they do happen," said lead author Lynn R. Sykes regarding the study and earthquake risk. "This study takes a more realistic look at the possibility of larger ones, and why earthquakes concentrate in certain places.

“To understand risk, you have to multiply hazard by assets, and vulnerability. When you factor that in, our risk is high. Too much attention has been paid to the level of hazard, and not enough to the risk. Earthquake hazard is about the same today as in 1609 when Henry Hudson sailed up the River. But earthquake risk is much, much higher today, since the number of people, assets and their vulnerability are so much greater."

Posted by Josh Hill.

http://www.eurekalert.org/pub_releases/2008-08/teia-eme082108.php