Monday, March 21, 2011

Earthquake Risk, Faults, Indian Point

Some people who seem to know what they're talking about think that the risk of an earthquake damaging the Indian Point nuke plants isn't worth worrying about. On the other hand, the Nuclear Regulatory Commission says the odds of an earthquake compromising the safety of Indian Point are 1,000 to 1 -- a long shot, certainly, but far from impossible.

Greg Clary wrote about it in today's Journal News.

At issue are a couple of fault lines that run near the plant, including the Ramapo faults. Here's what Greg reported:

The fault is actually a geological braid of fault lines running from the area of Clinton, N.J., to a mile or so west of the Buchanan nuclear plant, where it intersects with a second line that recent discoverers say runs between Stamford, Conn., and Peekskill....

But the U.S. Geological Survey — one of the nation's foremost research labs — said geologic evidence about the Ramapo Fault is "insufficient to demonstrate the existence of tectonic faulting or ... slip or deformation."

It didn't even include the fault in calculations of earthquake hazards in 2008.

Geology professor Alec Gates put it more succinctly: "The Ramapo Fault is dead," said Gates, chairman of Earth and environmental sciences at Rutgers University. "It was a big fault in the old days, but not anymore."...

What differentiates this region from more earthquake-prone areas, experts say, is that it lies in the middle of the North American Plate, a tectonic slab that encompasses North America to the Pacific Ocean, including Greenland, Cuba, the Bahamas, and parts of Siberia and Iceland.

"It's not a plate boundary; that's the primary reason you don't have activity and that it's hard to predict activity," said Paul Olsen, a professor of Earth and Environmental Sciences at Columbia University and a member of the National Academy of Sciences. "The formation of the Ramapo Fault was at least 300 million years ago. Most of the earthquakes around here have nothing to do with it."

Earthquake activity is greatest when boundaries of plate grind up against each other, pushing until one slips and the resulting movement accelerates out from the point until its energy dies out.

Earthquakes in the New York City metropolitan region don't rise very high on the Richter scale; the worst was a magnitude 5.2 event in 1884 that started in Far Rockaway, N.Y., and toppled chimneys in Suffern. The bigger ones are not that frequent.

Lamont-Doherty experts say the public should expect a magnitude 6.0 earthquake every 670 years, a 7.0 event every 3,400 years."

A few key points:

1. the Ramapo fault and its proximity to Indian Point might be irrelevant.

2. There are plenty of other active faults nearby -- one near Far Rockaway, for example, and another, which Greg doesn't mention, in Ardsley; it produced a magnitude 4.0 quake in 1985.

3. We can expect a magnitude 6 quake every 670 years and a 7 quake every 3,400 years. We may well be due for either of those.

But Greg also writes this, which I found worrisome:

The NRC's estimates for Indian Point, based on ground acceleration of earthquake energy, estimates there is a 1 in 1,000 chance that the reactors couldn't be shut down safely after an earthquake in this region.

What's comparable? The odds of catching a foul ball at a major league baseball game at a bit worse than 1 in 1,000. And yet everyone who goes to a ball game thinks they have a chance.

Labels: ,


Post a Comment

<< Home

eXTReMe Tracker