ARE EARTHQUAKES IN THE MASSENA, NEW YORK AREA RELATED TO THE GLOUCESTER AND WINCHESTER SPRINGS FAULTS?

The Massena, New York area located in the St. Lawrence Valley in northern New York has been the site of significant earthquake activity. On September 5, 1944 an earthquake of Intensity VIII on the Modified Mercalli Scale shook the Massena-Cornwall area. This was the largest earthquake to occur in New York State and its location in a populated region caused damage estimated at $18,000,000. On July 4, 1981 a magnitude 3.3 earthquake shook the Massena area and in the next few days, 17 additional earthquakes occurred. During the past five years five more earthquakes have occurred in the area.

Geologic studies done immediately after the Massena 1944 earthquake found no surface evidence of any major fault in the area. However, more recent studies indicate individual faults of the Ottawa-Bonnechere graben extended into the Massena area. Some recent earthquakes in the Massena area have epicenters that lie very near extensions of these faults (Gloucester and Winchester Springs).

The geologic structure of depth beneath the Massena area is not well understood. Seismic studies indicate a crustal thickness of 36 Km with two layers, an upper layer of 17.3 Km and at a lower layer of 18.7 Km thickness. Focal depth studies place the hypocenters at depths of 18 to 20 Km near the boundary between the two layers.

On March 17, 2004 two small earthquakes occurred that were aligned along the Winchester Springs fault. These earthquakes together with prior earthquakes in the area along the Winchester Springs and Gloucester faults suggest a possible correlation. Since the earthquake hypocenters occur in the Precambrian basement it is possible that the Winchester Springs and Gloucester faults are controlled by faulting at depth in the Precambrian.