3. Gravimetry

3.1 Basic principle

Gravimetry is the study of variations in the gravity field at the surface of the ground. Figure 1 shows the variation in the vertical component of the gravity field anomaly due to the presence in the subsoil of a cavity 6 m in diameter whose roof is 2 m deep in homogeneous soil with a density of 2,000 kg/m ³ . Two curves are shown, one for a spherical cavity (solid line), the other for a cylindrical cavity with an axis perpendicular to the plane of the figure (dashed line)....