GATE - Geophysics

Exam Syllabus

Part A: Common Section

Earth and planetary system – Terrestrial planets and moons of the solar system; size, shape, internal structure, and composition of the earth; plate tectonics – relationship with earthquakes, the concept of isostasy; propagation of body waves in the earth’s interior; Heat flow within the earth; structure, and thickness, Gravitational field of the Earth; geomagnetism and paleomagnetism; continental drift;, volcanism and mountain building; continental and oceanic crust – composition, elements of seismology – body and surface waves

Weathering and soil formation: The topic includes landforms created by glacier, river, wind, ocean, and volcanoes.

Basic structural geology – Stress, strain, and material response; nomenclature and classification of folds and faults, brittle and ductile deformation.

Crystallography – Basic crystal symmetry and concept of point groups. Mineralogy – silicate crystal structure and determinative mineralogy of common rock-forming minerals.

Petrology of common igneous, sedimentary and metamorphic rocks.

Geological time scale; Geochronology and absolute time. Mineral, coal, and petroleum resources of India, Stratigraphic principles; major stratigraphic divisions of India.

Introduction to remote sensing

Engineering properties of rocks and soils

Elements of hydrogeology

Principles and applications of gravity, magnetic, electrical, electromagnetic, seismic, and radiometric methods of prospecting for oil, mineral, and groundwater; introductory well logging.

Part B (Section-2): Geophysics

Solid-Earth Geophysics – The earth as a planet; different motions of the earth; gravity field of the earth, Clairaut’s theorem, size and shape of earth; geomagnetic field, paleomagnetism; Geothermics and heat flow; seismology and interior of the earth; variation of density, velocity, pressure, temperature, electrical and magnetic properties of the earth.

Geodesy – Gravitational Field of the Earth; Geoid; Ellipsoid; Geodetic Reference Systems; Datum; Everest (1830) and WGS 84 (1984) systems; GPS and DGPS; Levelling and Surveying.

Earthquake Seismology – Elements of elasticity theory- stress and strain tensors, Generalized Hooke’s Law; Body and Surface Waves; Rotational, dilatational, irrational, and equivolumnal waves; Inhomogeneous and evanescent waves and bounded waves; Eikonal Equation and Ray theory; earthquakes-causes and measurements, magnitude and intensity, focal mechanisms; earthquake quantification, source characteristics, seismotectonic, and seismic hazards; digital seismographs, Elements of Seismic Tomography; Reflection, and refraction of elastic waves; Earthquake statistics, wave propagation in elastic media, quantifying earthquake source from seismological data.

Potential and Time-Varying Fields – Scalar and vector potential fields; cylindrical, and spherical polar coordinates; Green’s theorem; Image theory; Laplace, Maxwell, and Helmholtz equations for solution of different types of boundary value problems in Cartesian; integral equations in potential and time-varying field theory.

Gravity Methods – Absolute and relative gravity measurements; Gravimeters; Land, airborne, shipborne, and bore-hole gravity surveys; Tensorial Gravity sensors and surveys; various corrections for gravity data reduction – free air, Bouguer, and isostatic anomalies; density estimates of rocks; regional and residual gravity separation; the principle of equivalent stratum; data enhancement techniques, upward and downward continuation; derivative maps, wavelength filtering; preparation and analysis of gravity maps; gravity anomalies and their interpretation – anomalies due to geometrical and irregular shaped bodies, depth rules, calculation of mass.

Magnetic Methods – Elements of Earth’s magnetic field, units of measurement, magnetic susceptibility of rocks and measurements, magnetometers and magnetic gradiometers, Land, airborne, and marine magnetic and magnetic gradiometer surveys, Various corrections applied to magnetic data, IGRF, Reduction to Pole transformation, Poisson’s relation of gravity and magnetic potential field, preparation of magnetic maps, upward and downward continuation, magnetic anomalies due to geometrical and irregular shaped bodies; Image processing concepts in the processing of magnetic anomaly maps; Depth rules; Interpretation of processed magnetic anomaly data; derivative, analytic signal and Euler Depth Solutions. Applications of gravity and magnetic methods for mineral and oil exploration.

Electrical Methods – Conduction of electricity through rocks, electrical conductivities of metals, nonmetals, rock-forming minerals, and different rocks, concepts of D.C. resistivity measurement and depth of investigation; Apparent Resistivity and Apparent Chargeability, Concept of Negative Apparent Resistivity and Negative Apparent Chargeability; Theory of Reciprocity, Sounding and Profiling, Various electrode arrangements, application of linear filter theory, Sounding curves over multi-layered earth, Dar-Zarrouk parameters, reduction of layers, Triangle of anisotropy, interpretation of resistivity field data, Principles of equivalence and suppression, self-potential method and its origin; Electrical Resistivity Tomography (ERT); Induced polarization, time and frequency domain IP measurements; interpretation and applications of SP, resistivity and IP data sets for ground-water exploration, mineral exploration, environmental and engineering applications.

Electromagnetic Methods – Geo-electromagnetic spectrum; Biot Savart’s Law; Maxwell’s Equation, Helmholtz Equation, Basic concept of EM induction in the earth, Skin-depth, elliptic polarization, in-phase and quadrature components, phasor diagrams; Response function and response parameters; Ground and Airborne Methods, measurements in different source-receiver configurations; Earth’s natural electromagnetic methods-telluric, geomagnetic depth sounding and magnetotellurics; Electromagnetic profiling and Sounding, Time domain EM method; EM scale modeling, processing of EM data and interpretation; Ground Penetrating Radar (GPR) Methods; Effect of conducting overburden; Geological applications including groundwater, mineral environmental and hydrocarbon exploration.

Seismic Methods – Elastic properties of earth materials; Reflection, refraction, and CDP surveys; land and marine seismic sources, generation and propagation of elastic waves, velocity–depth models, geophones, hydrophones, digital recording systems, digital formats, field layouts, seismic noise and noise profile analysis, optimum geophone grouping, noise cancellation by shot and geophone arrays, processing and interpretation; CDP stacking charts, binning, filtering, static and dynamic corrections, Digital seismic data processing, Reservoir geophysics- Rock Physics and Petrophysics, seismic deconvolution, and migration methods, attribute analysis, 2D, 3D and 4D seismic data acquisition, bright and dim spots, seismic stratigraphy, high resolution seismic, VSP, AVO, multi-component seismic and seismic interferometry. Geophysical Survey Design.

Geophysical Signal Processing – sampling theorem, Nyquist frequency, aliasing, Fourier series, periodic waveform, Fourier and Hilbert transform, Z-transform and wavelet transform; power spectrum, delta function, autocorrelation, cross-correlation, convolution, deconvolution, principles of digital filters, windows, poles, and zeros.

Geophysical Well Logging – Principles and techniques of geophysical well-logging, SP, resistivity, induction, gamma ray, neutron, density, sonic, temperature, dip meter, caliper, nuclear magnetic resonance- longitudinal and transverse relaxation, CPMG sequence, porosity characterization, cement bond logging, micro-logs. Pulsed Neutron Devices and Spectroscopy Multi-Array and Triaxial Induction Devices; Quantitative evaluation of formations from good logs; Logging while drilling; High angle and horizontal wells; Clay Quantification; Lithology and Porosity Estimation; Saturation and Permeability Estimation; application of borehole geophysics in groundwater, mineral and oil exploration.

Radioactive Methods – Prospecting and assaying of mineral (radioactive and non-radioactive) deposits, half-life, decay constant, radioactive equilibrium, G M counter, scintillation detector, semiconductor devices, application of radiometric for exploration, assaying, and radioactive waste disposal.

Geophysical Inversion – Basic concepts of forward and inverse problems, Ill-posedness of inverse problems, condition number, non-uniqueness and stability of solutions; L1, L2, and Lp norms, overdetermined, underdetermined and mixed determined inverse problems, quasi-linear and nonlinear methods including Tikhonov’s regularization method, Singular Value Decomposition, Backus-Gilbert method, simulated annealing, genetic algorithms, swarm intelligence, machine learning, and artificial neural networks. Statistics of misfit and likelihood, Bayesian construction of posterior probabilities, sparsity promoting L1 optimization. Ambiguity and uncertainty in geophysical interpretation.