EARTHQUAKES IN NORTHERN NEW YORK AND THE POTSDAM SEISMIC NETWORK

The Lamont-Doherty Cooperative Seismograph Network (LCSN) monitors earthquakes in eastern United States and consist of four nodes located at SUNY Potsdam, New York, Middlebury College, Vermont, Delaware Geological Survey and the LCSN at Palisades, New York. The Potsdam Node, located in the St. Lawrence Valley and Northwest Adirondacks consists of seven short-period vertical seismic field stations, one three- component broadband station and a long period vertical Press-Ewing seismometer installed in the basement of the Geology Department, Timerman Hall. Another short-period station is presently being installed at Mt. Arab, in the Adirondacks. The seismic network is operated by students who change records each day, repair and maintain seismic stations and heliocorders and locate local earthquakes.

The seven short-period seismic field stations are located in a belt of earthquakes extending from the Adirondacks across the St. Lawrence Valley into Western Quebec. Most of the earthquakes recorded by the short period network occur in this zone. During the past two years several earthquakes have been detected in this zone including the Au Sable Forks 5.2 earthquake of April 20, 2001. Gravity studies at the epicenter of the Au Sable Forks earthquake reveal a steep gravity gradient caused by a north-south trending fault that triggered the earthquake.

Gravity and magnetic investigations have been conducted in the epicentral regions of several local earthquakes in the Adirondacks. These studies indicate that both gravity and magnetic anomalies occur in the epicentral regions that may be related to faults that are triggering the earthquakes. Results of the investigations of 4 earthquakes (Au Sable Forks, Goodnow, Raquette Lake and Blue Mt. Lake earthquake swarms) are presented.

The long period Press-Ewing vertical seismometer on the basement floor in the Geology Department detects earthquakes of magnitude 6 or greater from around the World. During the last year teleseisms have been recorded from Japan, New Zealand, Indonesia, Sibera and Aleutians.