All materials in the earth influence the local gravitational force, g. While the large mass of the mantle and core account for the majority of the gravitational pull on earth, variations in near surface rock densities produce variations in g on the order of 10 -5. Surface gravity measurements are affected by the earth’s elllipticity, lunar tidal forces and local geography. Compensating for these factors requires precise geographical information; thankfully, recent advances in GPS technology has dramatically reduced these costs.
SJ Geophysics Ltd. employs Scintrex Autograv CG-3 gravity meters to make precise measurements of the gravitational field. Back in the office, gravity data is processed and can be inverted (using UBC-GIF inversion software) to produce a 3D model of the subsurface density distribution.
Applications
- Mapping large mineral deposits
- Geological mapping
- Locating subsurface caverns
- Locating contacts between geologic units of differing mass and density
