Geoph. 511: Part 1: Gravity and Magnetic Methods
A - Gravity Methods: Introduction - Fundamental principles: (Newton’s law - Gravitational acceleration - Earth’s mass and density - Gravitational potential - Rock densities - Normal spheroid and geiod - Gravity measurements and data reduction: (Absolute measurements - Relative measurements – Gravimeters - Field operations - Reduction of gravity data - Field determination of density) - Isostasy and crustal thickness: (Concept of isostasy - Nature’s isostatic experiment - Testing isostasy by gravity measurements - Isostatic rebound and the viscosity of the mantle - Depth of compensation and the “ Moho “ - Regions of uncompensated masses) - Analysis and interpretation of gravity data: (Ambiguity in gravity interpretation - Isolation of anomalies and analytic continuation of fields - Interpretation by models - Use of computational aids in interpretation) - Gravity anomalies and geological structures: (Granite and salt structures - Rift valleys and sedimentary basins - Structure of coastal margins - Oceanic ridges - Trenches - Regional geology and tectonics).
B - Magnetic Methods: Introduction - Fundamental principles: (Magnetic fields - Intensity of magnetization - Magnetic susceptibility and permeability - Dipole field – Diamagnetism – Paramagnetism - Ferromagnetism - Common magnetic series) - The earth’s magnetic field: (Geomagnetic elements - Non dipole field - Diurnal and secular variations - Origin of the main field - Reversals of geomagnetic field) - Magnetization of rocks: (Induced magnetization and bulk susceptibility - Magnetic anisotropy and rock fabric - Remanent magnetization and iconisberger ratio of rocks) - Magnetic surveying and interpretation techniques: (Magnetic measurements over land and sea - Airborne surveys for regional geology and tectonics) - Interpretation of magnetic data: (Qualitative and quantitative interpretation - Depth estimates from magnetic profiles) - Magnetic mapping of geological structures: (Basement mapping under sedimentary cover - Mapping of intrusive and extrusive).
Geoph. 511: Part 2: Radiometric and Geothermal Methods
(a) Radiometric Methods: Principles of radioactivity: (Constituents of nucleus - Nuclear disintigrations - Radioactive decay processes - Radioactive equilibrium - Radioactivity of rocks and minerals - Units) - Instruments: (Ionization chamber - Geiger counter - Muller counter - Scintillation meter - Gamma - ray spectrometer - Calibration of instruments) - Field operations and interpretation: (The use of radiometry in age dating - Distinguishing various rock types and mapping).
(b) Geothermal methods: (Thermal properties of rocks - Temperatures within the Earth) - Terrestrial heat flow: (Heat flow measurements - Equality of continental and oceanic heat flow - Regions of anomalous heat flow) - Thermal prospecting methods: (Measuring techniques) - Example: (Sulphide ore deposits prospecting - Thermal water and hot vapour zones - Salt and granite structures - Lithology information from temperature logs).
Geoph. 512: Part 1: Seismic Reflection Methods
Introduction - Elements of seismic surveying: (Seismic waves - Elastic constants - Reflection surveying) - Geometry of reflected ray paths: (Single horizontal reflectors - Multiple horizontal reflectors - Dipping reflectors - Ray paths of multiple reflections) - Multichannel reflection profiling - The reflection seismogram - Presentation of reflection survey data - Survey design parameters - Time corrections applied to seismic traces - Reflection data processing: (Frequency filtering - Inverse filtering - Velocity filtering) - Migration of reflection data - Interpretation: (Structural analysis – Stratigraphic analysis - Seismic modeling).
Geoph. 512: Part 2: Seismic Refraction Methods
Basic Principles of Seismic Refraction: Wavefronts and ray paths - Emergence angles – Time distance curves: (Slope angle – Slope - Ray parameter - Apparent velocity) - Snell’s law of refraction - Critical refraction – Huygens’s principle - Fermat’s principle – Diffraction.
Straight Ray paths in Layered Media - Planar interfaces: Single layer refraction paths - Two layers horizontal interface problem - Faulted planar interfaces - Hidden layer problem - Single dipping interface refraction profile - The multi - layered problem.
Straight Ray paths in Layered media - Irregular interfaces: Construction of refracting boundaries: (Delay time method - Wavefront method - Plus and Minus method - Hales method - GRM method) - True velocity calculations.
Theory of Curved Ray paths: Introduction to the theory of curved paths - Linear distribution of velocity - Theoretical idealization of curved ray path in velocity gradient medium - Basic principles of convergency of overtaking time - Distance curves - Interpretation of seismic refraction data in vertical velocity gradient medium.
Seismic Refraction Data Corrections: Elevation corrections - Computation procedures of correction for penetration of diving wave into velocity gradient medium.
Transmission of diving waves through inhomogeneous gradient medium.
Geoph. 513: Part 1: Geoelectric Methods
Introduction - Fundamental principles: (Electrical properties of rocks and minerals - Fundamentals of the current flow in the earth - Electrical potentials and conductivities -Potential and current distribution in a homogeneous medium and across a boundary) - Methods of geoelectricity: (Methods using natural electrical sources - Methods using artificial electrical sources) - Earth resistivity methods: (Apparent and true resistivity - Electrode configurations - Electrical sounding and profiling - Resistivity survey instruments) - Application and interpretation of resistivity data: (Mapping of layered horizontal structures - Ambiguity in resistivity interpretation - Mapping of vertical structures - Interpretation of resistivity maps) - SP, IP and magnetotelluric methods: (Field procedure and interpretation of self potential data - Origin and characteristics of magnetotelluric field and telluric currents - Field procedures and interpretation of magnetotelluric fields - Sources of induced polarization effects and measurements - Interpretation of IP fields).
Geoph. 513: Part 2: Well Logging Methods
Introduction: (Importance of well logging in prospecting for water, hydrocarbons, minerals and ore deposits) - Applications of SP logs: (Identification of lithology - Determination of ore deposits - Determination of depositional environments - Determination of volume of shale content - Determination of formation water resistivity) - Applications of GR log: (Identification of lithology - Determination of volume of shale content - Well to well correlation) - Applications of NGS logs: (Identification of lithology: Evaporite environment - Sand and shale series - Carbonate series - Identification of unconformity surface - Determination of igneous rocks - Determination of organic content).
Geoph. 514: Field / Practical Course
Part 1: Practical exercises in gravity, magnetic, seismic refraction and geoelectric methods.
Part 2: Practical Exercises in radiometric, geothermal, seismic reflection and well logging methods.