Ancient fault in New York awakens with rare earthquake
A small earthquake shook upstate New York on an ancient fault that occasionally flares up, producing a brief but noticeable shake in the area.
The U.S. Geological Survey (USGS) detected a magnitude 2.6 earthquake Monday at 11:40 p.m. ET, just outside Chazy, about 25 miles south of Montreal, at a shallow depth of about five miles.
The earthquake occurred far from any tectonic plate boundaries, deep within the North American plate, making it a rare intraplate earthquake.
Such tremors are rare in the northeastern United States, where ancient faults only occasionally release accumulated stresses.
The shaking was lightly felt in the Lake Champlain Valley, including Plattsburgh, New York, and Alburgh, Vermont, where residents reported rapid shaking lasting only a few seconds. More than 100 residents reported feeling tremors to the USGS.
This earthquake is unusual because the region is located far from plate boundaries and its ancient faults rarely release accumulated stresses.
The USGS noted that earthquakes of this magnitude are unusual, but not unheard of along fault zones in the northern Appalachians.
No injuries or damage were reported; however, local emergency officials advised homeowners to inspect their foundations and outbuildings for cracks as a precaution.
The earthquake was detected outside Chazy, New York, home to a few hundred people. More than 100 people reported tremors to USGS
The earthquake shows how even deep, ancient faults can produce noticeable shaking far from plate boundaries.
The Adirondack region has experienced several notable earthquakes over the years.
The largest on record occurred in 1944, a magnitude 5.8 earthquake that caused approximately $20 million in damage in Massena, New York, and Cornwall, Ontario.
A magnitude 4.9 temblor in 1983 caused minor damage in a remote part of the southern Adirondacks, and a magnitude 5.0 earthquake near Plattsburgh, New York, on April 20, 2002, also produced localized damage.
Earthquakes of moderate damage typically occur somewhere in the region every few decades, while more minor quakes are felt every three to four years.
Although Monday’s earthquake was small, an assessment from Michigan Tech University showed that people generally do not feel earthquakes of magnitude 2.5 or less.
Those from 2.5 to 5.4 are often felt but only cause minor damage.
The area near Chazy is located within the Champlain Thrust Fault Zone, a significant geological feature that extends from southern Quebec to western Vermont and eastern New York.
The earthquake struck about five kilometers from Chazy on Monday at 11:40 p.m.
This east-dipping thrust fault was primarily active during the Taconic Orogeny of the Ordovician period, approximately 450 million years ago, and experienced reactivation during later tectonic events, such as the Acadian Orogeny in the Devonian.
Although the Champlain Thrust is an ancient fault, it is not considered dormant.
Seismic activity in the region, including the recent 2.6 magnitude earthquake near Chazy, suggests that these faults can still produce notable shaking, although rarely.
