Advanced Geophysical Prospecting I




1. Seismic Surveys

    1.1 Introduction

    1.2 Elastic waves and propagation parameters

        1.2.1   Body and surface waves
        1.2.2   Pulse frequency and attenuation characteristcs
        1.2.3   Reflection, refraction and diffraction waves

    1.3 Seismic velocities in rocks

        1.3.1   Factors affecting velocity
        1.3.2   Velocity-density and velocity-porosity relationships
        1.3.3   Velocity data

    1.4 Reflection surveying

        1.4.1   Introduction
        1.4.2   Data acquisition in shallow seismics
                     (1) Seismic sources
                     (2) Geophones and arrays
                     (3) Seismographs and filters
                     (4) Field parameters
        1.4.3   Reflection geometry and the concept of NMO
                     (1) Horizontal reflectors
                     (2) Dipping reflector
        1.4.4   Common-depth point (CDP) technique
        1.4.5   Static and dynamic corrections
                     (1) Static corrections
                     (2) Dynamic or NMO corrections
        1.4.6   Determination of average velocities
                     (1)T2 - X2 method
                     (2) Velocity-spectrum method
                     (3) Well-shooting and CVL methods
        1.4.7   Synthesis of reflection traces
        1.4.8   Processing of reflection data
        1.4.9   Migration of reflection points
        1.4.10 Shallow reflection profiling : CDP and COF techniques
                     (1) Optimum offset technique
        1.4.11 Resolution limits in reflection mapping
        1.4.12 Applications to environmental and engineering problems
                     (1) Mapping of fracture zones
                     (2) Reflection profiling in groundwater studies
                     (3) Delineation of bedrock valleys
                     (4) Detection of shallow faults and cavities

    1.5 Refraction surveying

        1.5.1   Introduction
        1.5.2   Mapping of horizontal  interfaces : intercept time method
        1.5.3   Horizontal versus vertical velocity changes
        1.5.4   Mapping of faults and steep contacts
        1.5.5   Mapping of dipping interfaces
        1.5.6   Mapping irregular (non-planar) interfaces
                     (1) Technique of phantom arrivals
                     (2) Separation of delay times
                     (3) The plus-minus method
        1.5.7   Interpretation by generalized reciprocal method
        1.5.8   Refraction survey data acquisition
        1.5.9   Applicability and limitations of the refraction method
        1.5.10 Environmental and engineering applications
                     (1) Velocity as a guide to rock strength
                     (2) Detection of potential collapse features
                     (3) Mapping of buried ancient ditch
                     (4) Mapping of gravel and sand deposits
                     (5) Dam site investigations
 

2. Self-Potential Surveying

    2.1 Introduction

    2.2 Origin of self-potentials

            (1) Electrofiltration potential
            (2) Thermoelectric potential
            (3) Electrochemical  potential
            (4) Mineralization potential

    2.3 Data acquisition and noise suppression

        2.3.1   Field procedure
        2.3.2   Noise suppression and data enhancement

    2.4 Interpretation of SP data

    2.5 Applications to environmental and engineering problems

        2.5.1   Seepage flow in landslide body
        2.5.2   Seepage flow in dams and reservoir floors
        2.5.3   Delineation of groundwater flow
        2.5.4   Studies of geothermal fluid flow
 
 

3. Resistivity and induced polarization surveys

    3.1 Introduction

    3.2 Electrical resistivity of earth materials

    3.3 Theory of current flow in the ground

        3.3.1   Potential distribution in homogeneous ground
        3.3.2   Apparent resistivity and electrode configurations
        3.3.3   Potential and current distribution across a boundary
        3.3.4   Computation of apparent resistivity by linear filters

    3.4 Field procedures and selection of electrode array

        3.4.1   Electric sounding and profiling procedures
                     (1) Vertical electric sounding
                     (2) Electric profiling
        3.4.2   Selecting an array for a particular application

    3.5 Resistivity instruments and electrode layouts

    3.6 Interpretation of resistivity data

        3.6.1   General
        3.6.2   Interpretation by master curves and auxiliary graphs
        3.6.3   Forward and inverse modeling techniques
        3.6.4   Ambiguity in interpretation of sounding curves
        3.6.5   Interpretation of lateral resistivity contacts
        3.6.6   Interpretation of combined electric and sounding

    3.7 Applications of resistivity surveys

        3.7.1   Groundwater exploration and water quality
                     (1) Delineation of acquifer boundaries in sedimentary layers
                     (2) Groundwater in fissured  rocks
                     (3) Mapping boundaries of saline groundwater
        3.7.2   Examples of environmental and engineering applications
                     (1) Mapping of chemical pollution plumes
                     (2) Delineation of water-saturated zones in landslide bodies
                     (3) Location of permafrost zones
                     (4) Location archaeological objects
                     (5) Location of cavities and voids
        3.7.3   Resistivity characteristics of geothermal fluids

    3.8 Induced polarization method

        3.8.1   Principles
        3.8.2   Time-domain and frequency-domain measurements
        3.8.3   Data acquisition
                     (1) Equipment
                     (2) Field procedures
        3.8.4   Interpretation of IP data
        3.8.5   Examples of applications to environmental studies
                     (1) Evaluation of aquifer potential
                     (2) Investigation of domestic waste dump
                     (3) Mapping of industrial contamination
 

4. Electromagnetic surveys

    4.1 Introduction

    4.2 Theory of propagation of EM fields

        4.2.1   Fundamental quantities and field equations
        4.2.2   Attenuation of EM fields and depth penetration
        4.2.3   Phase relations and elliptic polarization of EM fields
                     (1) Phase relations
                     (2) Elliptic polarization of EM fields

    4.3 Classfication of EM mthods

            (1) Continuous wave field methods (frequency domain)
            (2) Transient field methods (time domain)
            (3) Magnetotelluric (MT) methods

    4.4 Continuous wave field methods (frequency-domain EM)

        4.4.1   VLF and VLF-R methods
                     (1) Conventional VLF
                     (2) VLF-resistivity method

        4.4.2   Horizontal loop (Slingram) method
        4.4.3   Ground conductivity meters
        4.4.4   Examples of applications to environmental problems
                     (1) Delineation of contamination plume from waste dumps
                     (2) Mapping industrial groundwater contamination
                     (3) Mapping soil salinity in farmland

    4.5 Transient-field methods (time-domain EM)

        4.5.1   Principles and operational designs
        4.5.2   Interpretation of TDEM data
        4.5.3   Examples of environmental studies
                     (1) Mapping of contamination plume at a landfill site
                     (2) Mapping of brine pockets at a waste repository site
        4.5.4   Nuclear magnetic resonance (NMR) method

    4.6 Interpretation of EM data

        4.6.1   Use of interpretational aids
        4.6.2   Ambiguity in EM interpretation

    4.7 Magnetotelluric methods

        4.7.1   Principles of MT sounding
        4.7.2   AMT and CSAMT methods
        4.7.3   Inversion of AMT data
        4.7.4   Examples of permafrost zones
                     (1) Mapping of permafrost zones
                     (2) AMT investigations in geothermal areas

    4.8 Radio imaging method (RIM)

        4.8.1   Principles and practices
        4.8.2   Example of imaging a fault zone

 
 
 
 
 
 
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