The gravity method involves measurement of the gravitational attraction exerted by the earth at a measurement station on the surface. The strength of the gravitational field is directly proportional to the mass and, therefore, the density of subsurface materials. Anomalies in the earth’s gravitational field result from lateral variations in the density of subsurface materials.
GEOVision geophysicists use the gravity method during hydrogeologic and engineering investigations to:
- Map regional geologic structure
- Map basement topography and sediment thickness
- Map basement fault zones
- Locate underground caverns
- Locate abandoned mine shafts
GEOVision geophysicists use LaCoste and Romberg Models G and D gravimeters when conducting gravity surveys. GEOVision uses a gravity processing system by Geosoft, Inc. to reduce gravity data. This computer package allows tidal corrections, drift corrections, latitude corrections, free-air corrections, Bouguer corrections, and digital terrain corrections to be made to the data after reduction of the gravity data, a Bouguer gravity contour map or profile is generated.
The data can then be modeled using forward and/or inverse modeling techniques. Currently, GEOVision geophysicists use the program GM-SYS by Northwest Geophysical Associates for forward and inverse modeling of gravity data. GEOVision also uses gravity software developed by University of California Riverside to reduce and model gravity data.