The Gravity method is used to measure subtle variations in the earth’s gravity field. These variations are related to subsurface material density and can be used to infer geologic structure. Gravity surveys can be conducted to:
Gravity surveys involve recording measurements of the earth’s gravity field across a survey area. Shallow subsurface features cause a minute change in the overall gravity field. Therefore, the measurements must be corrected for other effects on the data, such as the gravity influences of elevation, terrain, latitude, tidal effects, instrumental drift, etc. Once corrected, the data is gridded and displayed as a map or a series of profiles across the area. Since gravity is caused by mass, denser materials have stronger gravitational fields than less dense material. By using gravity data, a model may be created of the subsurface. The interpretation of gravity data may be used to map various geological structures including sedimentary basins, aquifers, and ore-bodies. The gravity method is often coupled with other datasets such as resistivity, electromagnetic, or seismic.
Gravity surveys are not affected by cultural features that confound other methods, such as metal objects or utilities. They are useful over extremely large survey areas.
Gravity data require extensive processing to apply varied corrections. Also, resultant models are non-unique and generally require some knowledge of the subsurface geology or additional data from other methods.