Understanding gravity gradients

Abstract

Summary: Gravity gradients often produce a complex pattern of anomalies over their sources. To understand this pattern and to aid in the interpretation of measured gravity gradient data, gravity gradient components of the full gradient tensor are computed starting with the basic gravitational potential, followed by computing the first derivatives and second derivatives of the potential. A diapiric salt model in a geologic setting similar to the US Gulf Coast is used for these computations; the results are displayed in color contour maps on which the model is projected for easy reference and interpretation of the data. Combinations of various gravity gradient components are also presented to enhance the anomalies associated with the model and to aid in the interpretation. It is also noticed that there are similarities between surface variations of the horizontal Gravity and Gravity Gradient components and subsurface variations of vertical Gravity and vertical Gravity Gradient (or anomalous Apparent Density) such as those observed in a borehole.