UNDERGRADUATE GRAVITY MAPPING IN NORTHERN NEW YORK

Some results of undergraduate research in gravity surveying conducted by students at SUNY Potsdam with support of the college summer undergraduate research program are presented. Students made 6,500 gravity measurements in northern New York in the Champlain and St. Lawrence valleys and the Northern Adirondacks. The gravity measurements were used to construct gravity maps that reveal gravity anomalies are related to the seismology, faults, and geology of the area.

The gravity maps of northern New York indicate a close correlation between earthquake epicenters and gravity gradients. The steep gradients of the anomalies suggest zones of weakness between rock types of varying density at shallow depths. This is supported by the common occurrence of shallow focus earthquakes in the area.

Gravity mapping in the AuSable Forks area reveals the location of a north-south trending fault that triggered the AuSable Forks 5.3 magnitude earthquake of 2002. Fault plane solutions of the earthquake agree with the fault trend indicated by gravity surveying.

Two prominent gravity anomalies occur in the Champlain Valley. A circular shaped gravity high located just north of Plattsburgh reveals the location of a high density pluton buried at a shallow depth. Just northwest of the Plattsburgh anomaly is a northeast-southwest trending gravity high along a fault possibly extending into the Precambrian basement.

In the Massena area site of significant earthquake activity, including the largest earthquake in New York (M=5.91 on Sept. 5, 1944,) gravity anomalies indicate faults or mafic intrusions related to earthquake foci.