In this project, we apply gravimetry to the mapping of interesting subterranean structures such as volcanoes, archeological sites, aquifers and other structures. Although gravity is a weak field, in some circumstances it is the only field that can be exploited to map subterranean structures. Volcanoes for example are a maze of tunnels and fissures with time dependent fluid flows that give rise to measurable gravitational fields. Aquifers similarly rise and fall and exhibit measureable time dependent gravitational fields. Archeological structures where access is restricted or forbidden can be mapped through the gravitational signal produced by underground rooms and cavities.
The mathematical problem we have to deal with is the inversion problem. There is not always a unique mapping of a source to the partial information we may have on the measured fields that result from the source. The question then is how to constrain the problem efficiently through more measurements, through assumed symmetry or other information we may have to enable a unique mapping. The fields we can measure for the problems we are concerned with are the 3 components of the gravitational field, the 3 components of the magnetic field, the five independent elements of the gravity gradient tensor, the five independent elements of the magnetic gradient tensor and the 3 independent elements of the scalar magnetic gradient tensor.