TIn gravity surveying, subsurface geology is investigated on the basis of variations in the Earth’s gravitational field arising from differences of density between subsurface rocks. An underlying concept is the idea of a rock unit of different density from its surroundings. This could represent a subsurface zone of anomalous mass that causes a localized anomaly in the gravitational field. The measurement of an absolute value of gravity is difficult and requires complex apparatus and a lengthy period of observation. The measurement of relative values of gravity, that is, the differences of gravity between locations, is simpler and is the standard procedure in gravity surveying. Gravimeters are basically spring balances carrying a constant mass. Variations in the weight of the mass caused by variations in gravity cause the length of the spring to vary and give a measure of the change in gravity. Special data processing and interpretation techniques are used to interpret the shape and amplitude of the anomalies in terms of subsurface geological structures.

Reference projects:

– Various gravity surveys for exploration purposes.