A comparative study of conventional arrays of resistivity prospecting with differential arrays

The second vertical derivative of gravity and magnetic potential are widely used in geophysical prospecting because of their better resolving power. In electrical prospecting these derivatives are not in use in spite of the fact that the derivatives can be directly measured in the field. The electrical prospecting offers a unique possibility to obtain the derivatives of potential in the field, in a desired direction which can be used for the computation of resistivity values. But most of the systems proposed for higher derivative measurement in sounding employ more than two source electrodes and current with high intensity which are difficult to work with. Hence, Murali et al. (1980) and Murali and Sharma (1982), have suggested a simple differential array for obtaining the second derivatives of potential both in the lateral and vertical directions. In this paper an attempt is made to test the level of accuracy of this differential array. The theoretical two layer dipole curves and the differential array field curves are compared with one another for the same P.jPl ratio. It has been shown from the results that this system is capable of detecting even very small changes in thickness oflayers and it yields useful data over two layered media. It has been proved that this system is superior over the other configurations.