Choice of Gravity Anomaly

Free-air, Residual, or Bouguer

If you are attempting to fit calculated values to observed values of gravity, you may use free-air, residual, or Bouguer gravity for the observed values. Note that the model calculations will include the contributions of the terrain above sea level using the selected densities. Therefore, if you use observed Bouguer anomaly values, you must specify the reduction density when you import the gravity data, which sets the density of the "Background" block to the Bouguer reduction density. Another option is to convert the densities of all blocks above sea level to density contrasts relative to the Bouguer reduction density. Typical densities for various rock types may be found in Clark (1966), Dobrin and Savit (1988), or many other references.

References cited here may be found in the References topic.