Subsurface Gravity Measurements and Density Mapping in the Mailaram Copper Mines, Andhra Pradesh, India*

Abstract

SATYANARAYANA MURTY, B.V., GHYASUDDIN, M. and VENKAT REDDY, P. 1982, Subsurface Gravity Measurements and Density Mapping in the Mailaram Copper Mines, Andhra Pradesh, India, Geophysical Prospecting 30, 444453.Gravity measurements were made in the Mailaram copper mines, Andhra Pradesh. The observations were distributed between the two shafts situated about 220 m apart and in the three levels up to a maximum depth of 100 m. Assuming a normal free-air gradient, average densities for the three layers were determined as 2.631, 2.604, and 2.823 g ~m -~, respectively. Upon incorporating the weighted mean density values from measurements on samples, the free-air gradients were found to be 0.315 mGal m-l for the second layer (i.e. between the first and second levels) and 0.2978 mGal mfor the third layer (i.e. between the second and third levels). The density variation map obtained from the gravity data, the deduced anomalies, the weighted mean density values from measurements on rock samples, and the varying free-air coefficients all suggest correspondence with the concentration of ore lodes.

A gravitational eye: a method for extracting maximum information from gravitational potentials

“…First of all, we need to see how analytic continuation works for the first radial derivative of the potential. From (9) we have that, on the data sphere,…”

“…From this we wish to find the radial derivative on a sphere of radius r, minus the same at r = 0. We start with the expansion of the radial component of gravity in (9) on the sphere of radius r. Subtracting off the same expansion, but evaluated at the centre of rotation (i.e. r = 0), gives the (noiseless) data on the sphere of radius r…”

“…While for most of these the survey is performed above the ground (either airborne or on the surface), some surveys are performed underground or within built structures. This includes applications such as mining [9], mine-shaft inspection [10], coalmine safety [11], tunnel wall inspection [12] and within boreholes for monitoring carbon capture and storage sites [13,14]. In this paper we consider a new sensing approach which could provide more information than traditional approaches, particularly in restricted environments such as underground, where the gravitating objects of interest could lie in any direction, including above the instrument.…”

Underground gravity survey in a coal mine

“…In the mines that are large or complex, additional base stations are included at every level or separated part of the mine, in order to connect measurements at all stations. Quality control of the underground gravity survey is achieved by repeated measurements at the base stations (Murty et al 1982).…”