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Gravity Method

The gravity method involves measuring the acceleration due to the earth's gravitational field. A gravity meter or gravimeter measures the variations in the earth's gravitational field. The variations in gravity are due to lateral changes in the density of the subsurface rocks in the vicinity of the measuring point. Because the the density variations are very small and uniform, the gravimeters are very sensitive and they measure one part in 100 million of the earth's gravity field (980 gals or 980,000 milligals) in units of milligals or microgals.


Bouger Gravity Anomaly Map of New Jersey

Contour interval: 5 mgals

GRAVITY MAP OF NJ

OFM 55, Bouguer Gravity Anomaly Map of New Jersey and Vicinity. Download PDF (541KB)

NJGS DIGITAL GEODATA SERIES DGS04-2 Bouguer Gravity Anomalies of New Jersey


Gravity Surveys are used for modeling the earth's crustal structure, for locating bedrock fractures, buried topographic valleys, subsurface voids such as abandoned mines, caverns, and sinkholes, and for determining overburden thickness and depth to bedrock.


Gravity anomaly map over an abandoned mine.

MINE SHAFT

A gravity profile from above map and its interpreted model.

GRAVITY MODEL

 


For more information on geophysical techniques, please refer to

Chapter 8 "Geophysical Techniques" of the NJDEP's Field Sampling Procedures Manual, 2005.

OFR 90-2 - Gravity Base Station Network in Northern New Jersey, Ghatge, Suhas L., and Jagel, Donald L., 1990, 39 p., Price $5.00 Download PDF (13.1MB)

OFR 91-1 - Detection of an Abandoned Mine using High-Resolution Geophysical Methods in Randolph Township, Morris County, New Jersey, Ghatge, Suhas L., and Waldner, Jeffrey S., 1991, 10 p., Price $5.00 Download PDF (3.49MB)

Microgravity Method for the Detection of Abandoned Shafts of the Schuyler Mine in Northeastern New Jersey, Ghatge Suhas L., 1993, Proceedings of the Symposium on the Application of Geophysics to Engineering and Environmental Problems (SAGEEP 1993), April 18-22, 1993, San Diego, California.,Vol. 1, pp. 195-207.

Microgravity Method for detection of Abandoned Mines in New Jersey, Ghatge, Suhas L., 1993, Bulletin of the Assoc. of Engineering Geologists, Vol XXX, No. 1, 1993, pp.79-85.


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Department of Environmental Protection
Geological and Water Survey
P. O. Box 420
Mail Code:29-01
Trenton, NJ 08625-0420

Phone: (609) 292-1185
FAX: (609) 633-1004