Gravity mapping of a subsurface cavity at Marulan, N.S.W.

Abstract

Application of the gravity method in the detection of underground cavities has been reported by several authors (Colley, 1963; Neumann, 1967; Butler, 1984). An air-filled cavity presents a density contrast equal to the density of host rocks which are usually formed by limestone or dolomite. Depending upon their age and depth of burial the density of these rocks may range from 2.2 to 2.8 gcm-3. A fully or partially water-filled cavity will present a smaller density contrast. According to Omnes (1977), the gravity method has gradually replaced the resistivity method and since 1971 has been the choice method for the detection of subsurface cavities in Europe.