Section A
Q1.
(a) (i) A Ground-Penetrating Radar (GPR) in monostatic mode recorded a two-way travel time of 0.2985 µs over a two-layered medium involving non-conducting dry soil of relative permittivity (epsilonr = 5), overlying water table. Find the depth of water table. (Consider velocity of light in vacuum, c to be 0.3 m/ns)
(a)
(ii) A Magneto-Telluric (MT) sounding over a layered earth medium has yielded an apparent resistivity,
hoa of 120 Omega-m at a time period, T of 0.1 s for an electric field amplitude of 10 mV/km. Compute the involved magnetic field amplitude in nT.
(b) (i) State the necessary and sufficient conditions for the origin of gravity and magnetic anomalies separately.
(b) (ii) On the basis of intensity of magnetic anomalies, distinguish between intra-basement and supra-basement anomalies. Specify their geological applications.
(c)
An electrical sounding experiment using Schlumberger configuration has resulted in identical Vertical Electrical Sounding (VES) curves for the following two geoelectrical sections, A and B. Hence, estimate the thickness of sandwiched bed of geoelectric section B.
Geoelectric Section A :
ho1 = 30 Omega-m;
ho2 = 10 Omega-m;
ho3 = 100 Omega-m; h1 = 3 m; h2 = 10 m; h3 ightarrow infty
Geoelectric Section B :
ho'_1 = 50 Omega-m;
ho'_2 = 25 Omega-m;
ho'_3 = 100 Omega-m; h'_1 = 5 m; h'_2 = ?; h'_3 ightarrow infty
