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Application of Surface Geophysics to Ground-water Investigations

U.S. Geological Survey, Techniques of Water-Resources Investigations, Book 2, Chapter D1

By A. A. R. Zhody, G. P. Eaton, and D. R. Mabey


Table of Contents

Abstract

Introduction

Design of geophysical surveys

Collection and reduction of geophysical data

Interpretation

The literature of exploration geophysics

Electrical methods, by A. A. R. Zohdy

Telluric current method

Magneto-telluric method

Spontaneous polarization and streaming potentials

Direct current-resistivity method

Definition and units of resistivity

Rock resistivities

Principles of the resistivity method

Electrode configuration

Wenner array

Lee-partitioning array

Schlumberger array

Dipole-dipole arrays

Electrical sounding and horizontal profiling

Comparison of Wenner, Schlumberger, and dipole-dipole measurements

Problem of defining probing depth

Advantages of using logarithmic coordinates

Geoelectric parameters

Types of electrical sounding curves over horizontally stratified media

Electrical sounding over laterally inhomogeneous media

Limitations of the resistivity method

Analysis of electrical sounding curves

Qualitative interpretation

Determination and use of total transverse resistance, T, from sounding curves

Determination of total longitudinal conductance, S, from sounding curves

Determination of average longitudinal resistivity, pL, from a sounding curve

Distortion of sounding curves by extraneous influences

Quantitative interpretation

Analytical methods of interpretation

Two-layer interpretation

Three-layer interpretation

Four-layer (or more) interpretation

Empirical and semi-empirical methods of interpretation

Moore´s cumulative resistivity method

Barnes´ layer method

Applications of resistivity surveys in ground-water studies

Mapping buried stream channels

Geothermal studies

Mapping fresh-salt water interfaces

Mapping the water table

Mapping clay layers

Electromagnetic methods

Induced polarization methods

Relationship between apparent chargeability and apparent resistivity

Induced polarization sounding and profiling

Applications of induced polarization in ground-water surveys

References cited

Seismology, by G. P. Eaton

Elementary principles

Reflection versus refraction shooting

Comparison of the refleotion and refraction seismic methods in practice

Seismic refraction measurement in hydrogeology

Effect of departures from the simple stratified model

The multilayered model

Effect of a regular increase of velocity with depth

Effect of dipping layer

Effect of a sloping ground surface

Effect of a buried steplike re-fractor

Effect of a discordant steep sided body

Effect of a thin refractor

Effect of a velocity inversion at depth

Effect of a refractor of irregular conflguration

Effect of lateral varying velocities

Corrections applied to seismic refraction measurements

Elevation correction

Weathered-layer correction

Errors in seismic refraction measure ments

Application of seismic refraction measurements in hydrogeology

Mapping buried channels

Measuring depths to the water table

Determining the groee stratigraphy of an aquifer

Mapping lateral facies variations in an aquifer

Estimating porosity from seismic wave-velocity values

References cited

Gravimetry, by G. P. Eaton

Reduction of gravity data

Latitude correction

Tidal correction

Altitude corrections

Free-air correction

Bouguer correction

Terrain correction

Drift correction

Regional gradient

Bouguer anomaly

Interpretation of gravity data

Ambiguity

Interpretation techniques

Significance and use of density meaeurements

Application of gravimetry to hydrogeology

Aquifer geometry

Estimating average total porosity Surface method

Borehole method

Effect of ground-water levels on gravity readings

References cited

Magnetic methods, by D. R. Mabey

Magnetic surveys

Magnetic properties

Design of magnetic surveys

Data reduction

Interpretation of magnetic data

Examples of magnetic surveys

Gem Valley, Idaho

Antelope Valley, California

References cited

Cost of geophysical surveys in 1970

Electrical methods

Gravity surveys

Seismic surveys

Magnetic surveys

 


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