Local Changes in Gravity Resulting From Deformation

The horizontal and vertical components of gravity change when tectonic stresses deform the earth because mass is redistributed relative to the gravity meter. We analyze the change in gravity resulting from deformation in a homogeneous elastic half-space. We derive expressions in closed form which give the change in horizontal and vertical components of gravity measured at the surface for any specified distribution of dislocations at depth. For example, the change in the vertical component of gravity observed by a gravity meter fixed in space above an infinitely long thrust fault is found to be proportional to the local change in height, whereas the change due to a spherically symmetric source of dilatation is zero. Analysis of the change in the horizontal component shows that error in measurements of uplift resulting from changes in level is negligible for these sources.