Question

How could electrical measurements (including equipotential lines) locate underground anomalies such as a cave, an ore body, a buried pipe, or a vein of minerals?

Answer 1

Ans: In Geophysics, Resistivity method is used in the study of horizontal and vertical discontinuities in the electrical properties of the ground, and also in the detection of 3D bodies of anomalous electrical conductivity.In the resistivity method, artificially we can generated electric currents are introduced into the ground and the resulting potential differences are measured at the surface. Deviations from the pattern of potential differences expected from homogeneous ground provide information on the form and electrical properties of subsurface inhomogeneities.

Basic concept of resistivity method is 2 current electrodes and 2 potential electrodes are used in that we can choose which electrode configuration is suitable its depend on the survey area. latest technique Electric Resistivity Tomography is used to measure both vertical and horizontal variation of the subsurface of earth, after processing its gives the Pseudo image subsurface of earth easy can identify the anomalies such as a cave, an ore body, a buried pipe, or a vein of minerals, each mineral different resistivity values (ohm-meters) easy can interpret which mineral presence of subsurface.

The resistivity of a material is defined as the resistance in ohms between the opposite faces of a unit cube of the material. it is given by

Reisitivity = R A/L

where R - resistance (ohm)

A- area of crosssection

L-length

Resistivity is the ohm-metre (ohm m) and the reciprocal of resistivity is termed conductivity (siemens / metre).