Scientists say a small earthquake was recorded Saturday morning in Putnam County, just a few miles north of the Westchester County border. A local newspaper, The Journal News, reported that area residents did not hear or feel anything. Those near the epicenter however, were startled out of their homes.
The earthquake around 10:45 a.m. was about 3 miles beneath the Appalachian Trail, in a heavily wooded area in Garrison. The Lamont-Doherty Cooperative Seismographic Network placed the 2.5-magnitude earthquake’s epicenter a few miles north of Peekskill in Westchester County. Nano Seeber is a research professor with Columbia University’s Lamont-Doherty Earth Observatory in Palisades, in Rockland County. He says the small quake was not along any fault lines.
“The Hudson Highlands is a belt of old crystalline rocks, meaning very old rocks that are part of the North American ‘basement’,” “And so these rigid, crystalline rocks seem to have a concentration of earthquakes.”
“Now the other important issue is that there is fault, it’s a very old fault, which bounds these rocks toward the southeast, toward the highly populated region,” says Seeber. “And this fault is called that Ramapo Fault and there is a concentration of earthquakes near this fault. And of course this is of great concern because there is a nuclear power plant as well along this fault.”
That nuclear power plant is Buchanan-based Indian Point, which sits along the Hudson River within viewing distance of Peekskill. Jerry Nappi is spokesman for Indian Point parent Entergy Nuclear.
“2.5 is actually more than 10,000 times below what Indian Point is built to withstand,” says Nappi. “So, in other words, Indian Point can withstand an earthquake that has 10,000 times more energy than that release from a 2.5 Richter level earthquake.”
And he adds:
“This particular event this past weekend was at such a low level that it didn’t trigger our seismic monitors to record the event,” Nappi says.
Seeber says earthquakes like the one in Garrison likely occur about 5-to-10 times a year throughout the Hudson Highlands, and, just as likely, are not felt. He says although small, there should be concern, not alarm, about the proximity to Indian Point.
“I am concerned, let’s put it that way,” says Seeber. “However, on the other hand, there’s no place on earth where you are absolutely free from earthquakes.”
He says it is then Indian Point’s job to mitigate earthquake risk. In May, the Nuclear Regulatory Commission issued a priority list for nuclear power plants when it comes to detailing earthquake risk, requiring more analysis about seismic risk from a number of plants, including Indian Point and Pilgrim, in Massachusetts. The required re-evaluation of seismic risk follows the March 2011 Fukushima nuclear accident in Japan.
Seeber says, as a seismologist, the earthquake is bit puzzling.
“There is significant earthquake hazard in this area,” Seeber says. “Now, when you combine that with the fact that we actually know much less about these earthquakes, in part because there’s fewer of them, there’s not much to study, let’s say, it then, the hazard is kind of increased by the fact that we can’t say much about it because we don’t understand basically why these earthquakes occur.”