List of top Geophysics Questions on Electrical Methods asked in GATE GG

If C1 & C2 and P1 & P2 are the pairs of current and potential electrodes in the Wenner (W) and Dipole-Dipole (DD) array configurations as shown in the figure below, then the fraction of the geometric factor for DD array that will be equal to half of that of W array is _______________ (rounded off to three decimal places). (Use n = 1 in DD array)

A vertical contact separating two resistive domains, \(\rho_1\) and \(\rho_2\) (with \(\rho_2 > \rho_1\)), is shown in the figure below, with the strike direction along X, the profile direction (perpendicular to strike) along Y - where the electric field component \(E_y\) is discontinuous across the contact - and depth along Z.

The magnitude of the discontinuity in the apparent resistivity, when the electric field, \(E\), is perpendicular to the strike, is

Which pairs of the following combinations of the H-, Q-, K- and A- type of resistivity sounding curves is/are NOT possible to generate four-layer models?

Among the given layered models, labelled as P, Q, R and S, which of the following pairs is/are NOT possible to distinguish according to the principle of equivalence?

Model parameters read off the figure -- (P): \(\rho_1 = 1\ \Omega\text{m}, h_1 = 10\ \text{m}\); \(\rho_2 = 100\ \Omega\text{m}, h_2 = 20\ \text{m}\); \(\rho_3 = 0\ \Omega\text{m}\).
(Q): \(\rho_1 = 5\ \Omega\text{m}, h_1 = 10\ \text{m}\); \(\rho_2 = 400\ \Omega\text{m}, h_2 = 5\ \text{m}\); \(\rho_3 = 0\ \Omega\text{m}\).
(R): \(\rho_1 = 40\ \Omega\text{m}, h_1 = 20\ \text{m}\); \(\rho_2 = 2\ \Omega\text{m}, h_2 = 10\ \text{m}\); \(\rho_3 = 100\ \Omega\text{m}\).
(S): \(\rho_1 = 30\ \Omega\text{m}\); \(\rho_2 = 3\ \Omega\text{m}, h_2 = 10\ \text{m}\), with \(h_1 = 5\ \text{m}\); \(\rho_3 = 100\ \Omega\text{m}\).