Gravity In Cave Exploration

A new method for the inversion of gravity data is introduced which is applicable to<br>regions with a limited number of allowable density values, such as uniform density bodies<br>set in a contrasting background. The method relies on geometrical constraints, such as<br>compactness, size, or shape of the anomalous body or bodies. A gridded forward model<br>is used to separate the geometry of the model from the density by dividing the earth into<br>regular prisms. Each prism is allowed only a limited number of density values: in this<br>case the density can be the background rock density or the cave density of 0. The prisms<br>are chosen to increase in size with depth in order to realistically model structures which<br>can be resolved with gravity data.<br>In this application, a genetic algorithm is used to find the best configuration of zero<br>density prisms to fit the data and is subject to geometrical constraints as mentioned<br>above. The method is described and tested on 2D synthetic models, then applied to<br>gravity data collected at the Indian Echo Caverns in Hershey, Pennsylvania.