November 21, 2012

Shake, rattle and roll

Plate compression causing earthquakes in North Country

AUSABLE FORKS — The chair starts to roll. The windows rattle.

Water in a glass ripples, and the table might jolt. A giant noise sometimes sounds like a train coming down the street.

But nothing visible is out there.



People in this region have come to recognize the hidden, unexpected shakes and groans of a moving Earth. 

Five midsize tremblors rumbled the region in the past month. They actually are the largest and most widely felt among 22 recorded in the region by Lamont-Doherty Cooperative Seismographic Network at Columbia University since mid-July. 

On Sept. 22, a 3.1-magnitude earthquake, measured on the Richter scale, sent waves rolling from an epicenter near Clarence, Quebec. 

On Oct. 4, a 2.5-magnitude jolt struck north of Huntingdon, Quebec, followed nearly an hour later by a 3.9 centered in Beloeil, some 65 miles to the northeast.

At 12:19 a.m. Oct. 10, a 3.9-magnitude quake centered about 21 miles north of Montreal could be felt across the area.

And at 7:12 p.m. Oct. 16, a 4.0-magnitude quake centered at Waterboro, Maine, reverberated across much of New England and Eastern New York. The shaking was clocked as a “V” out of “X” in what scientists measure using Roman numerals on the Modified Mercalli Intensity scale. Intensity is a measurement other than magnitude on the Richter scale to indicate damage. The evening’s rattling was felt as far south as Long Island. 


The seemingly tight sequence of events has left many in the area wondering what startled the usually quiet Earth underfoot: The Northeast section of North America doesn’t sit on the edge of a fault zone.

But there are ancient pieces of old faults.

Many of the ruptures stretch north to south, and other fractures — not faults — align at roughly 45-degree angles like great striations across the entire mass of Adirondack bedrock.

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