NORTHERN NEW YORK – WESTERN QUEBEC SEISMIC ZONE

The Northern New York – Western Quebec Seismic Zone extends from the Adirondack Mountains across the St. Lawrence Valley into Western Quebec. Historic earthquake data indicates the area is a region of moderate seismicity. The earthquake activity has been persistent for over 400 years. Most of the earthquakes in the zone have magnitudes ranging from 1 to 4 and shallow focal depths of less than 10 km. Fault plane solutions indicate the earthquakes are due to reverse faulting on northwest striking fault planes, however mapped faults in the area have a northeast trend. Even though most of the earthquakes are small, damaging earthquakes of magnitude greater than 5 occur such as the 5.9 magnitude Massena Cornwall (1944), 5.2 magnitude Goodnow earthquake (1983) and the 5.3 magnitude Au Sable Forks earthquakes (2002).

The Massena-Cornwall earthquake of September 5, 1944 was the largest earthquake to occur in New York State. It had a maximum intensity of VIII in the Massena-Cornwall area and was felt over an area of 148,000 km². The earthquake cause $2,000,000 damage ($8,000,000 today's dollars) and destroyed 90% of the chimneys in Massena.

The October 7, 1983 Goodnow earthquake had a maximum intensity of VII. The epicenter was located 12 miles northeast of Blue Mountain Lake in the central Adirondacks. No major damage resulted since the epicenter was located in a remote area.

The most recent damaging earthquake was the April 20, 2002 Au Sable Forks earthquake. The epicenter was located 7 km north of Au Sable Forks in the central Adirondacks. The earthquake had a maximum intensity of VII in the epicentral region and was felt over northwestern US and eastern Canada. Damage was done to roads, bridges, power substations, chimneys, cracked walls, and foundations. Over $16,000,000 damage was caused by the earthquake in Clinton and Essex Counties.