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Titleapplication of surface geophysics to ground-water investigations
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Table of Contents
	Design of geophysical surveys
	Collection and reduction of geophysical data
	The literature of exploration geophysics
	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 inhomogenous 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 semiempirical methods of interpretation of sounding curves
				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 method
		Relationship between apparent chargeability and apparent resistivity
		Induced polarization sounding and profiling
		Applications of induced polarization in ground-water surveys
	References cited
	Elementary principles
	Reflection versus refraction shooting
	Comparison of the reflection and refraction seismic methods in practice
	Seismic refraction measurements in hydrology
		Effect of departures from the simple stratified model
			The multilayered model
			Effect of a regular increase of velocity with depth
			Effect of dipping layers
			Effect of a sloping ground surface
			Effect of a buried steplike refractos
			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 configuration
			Effect of laterally varying velocities
	Corrections applied to seismic refraction measurements
	Elevation correction
	Weathered-layer correction
	Errors in seismic refraction measurements
	Applications of seismic refraction measurements in hydrogeology
		Mapping buried channels
		Measuring depths to the water table
		Determining the gross stratigraphy of an aquifer
		Mapping lateral facies variations in an aquifer
		Estimating porosity from seismic wave-velocity values
	References cited
	Reduction of gravity data
		Latitude correction
		Tidal correction
		Altitude correction
			Free-air correction
			Bouguer correction
			Terrain correction
			Drift correction
			Regional gradients
			Bouguer anomaly
	Interpretation of gravity data
		Interpretation techniques
		Significance and use of density measurements
	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 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
	Electrical methods
	Gravity surveys
	Seismic surveys
	Magnetic surveys
	Figure 1 - Diagram showing flow of telluric current over an anticline
	Figure 2 - Examples of electrode arrays for measuring x and y compnents of telluric field
	Figure 3 - Telluric map of the Aquatine basin, France
	Figure 4 - Diagram showing the relationship between a point of source current I (at origin of coordinates) in an isotropic medium of resistivity p and the potential V at any point P
	Figure 5 - Wenner, Lee-partitioning, and Schlumberger electrode arrays
	Figure 6 - Dipole-dipole arrays
	Figure 7 - Graph showing horizontal profile and interpretations over a shallow gravel deposit in California using Wenner array
	Figure 8 - Map of apparent resistivity near Campbell, Calif
	Figure 9 - Graph showing horizontal profiles over a buried stream channel using two electrode spacings: a = 30 feet and a = 60 feet
	Figure 10 - Electrode arrays
	Figure 11 - Graph showing comparison between four-layer Schlumberger and Wenner sounding curves
	Figure 12 - Correct displacements on a Schlumberger sounding curve and method of smoothing
	Figure 13 - Logarithmic plot of sounding curve
	Figure 14 - Linear plot of sounding curves
	Figure 15 - Columnar prism used in defining geoelectric parameters of a section
	Figure 16 - Comparison between two-layer Schlumberger curves for p2/p1 = 10 and 0.1; h1 = 1 meter for both curves
	Figure 17 - Comparison between two-layer azimuthal (or equatorial) and radial (or polar) sounding curves
	Figure 18 - Examples of the four types of three-layer Schlumberger sounding curves for three-layer Earth models
	Figure 19 - Examples of three of the eight possible types of Schlumberger sounding curves for four-layer Earth models
	Figure 20 - Examples of the variation of Schlumberger counding curves across a vertical contact at various azimuths
	Figure 21 - Examples of the variastion of Wenner sounding curves across a vertical contact at various azimuths
	Figure 22 - Examples of different types of curve equivalence
	Figure 23 - Map of apparent resistivity near Rome, Italy
	Figure 24 - Sections of apparent resistivity near Minidoka, Idaho.  Values on contour lines designate apparent resistivities in ohm-meters.  Snake River basalt thickens toward the north.
	Figure 25 - Graphical determination of total transverse resistance from a K-type, Schlumberger sounding curve
	Figure 26 - Profile of total transverse resistance values T in ohm-meters squared, near Minidoka, Idaho
	Figure 27 - Graphical determination of total longitudinal conductance S from an H-type Schlumberger sounding curve
	Figure 28 - Transformation of a Schlumberger KH-type curve into a polar dipole-dipole curve to evaluate ptmin = pL and H = SpL
	Figure 29 - Distortion of sounding cures by cusps caused by lateral inhomogeneities
	Figure 30 - Example of a narrow peak on a K-type curve, caused by the limited lateral extent of a resistive middle layer
	Figure 31 - Example of a distorted HK-Schlumberger curve and the method of correction
	Figure 32 - Examples of discontinuities on Schlumberger curves caused by a near vertical, dikelike structure
	Figure 33 - Two-layer master set of sounding curves for the Schlumberger array
	Figure 34 - Interpretation of a two-layer Schlumberger curve (p2/p1 = 5)
	Figure 35 - Interpretation of a three-layer Schlumberger H-type curve
	Figure 36 - Interpretation of a four-layer Schlumberger curve by the auxiliary point method using two three-layer curves
	Figure 37 - Map of San Jose area, California, showing areas studied
	Figure 38 - Map of apparent resistivity in Penitencia area, California
	Figure 39 - Resistivity profile and geologic section, Penitencia, Calif
	Figure 40 - Map of apparent resistivity near Campbell, Calif., obtained with Wenner array at a = 30 feet and shwoing location of Section AA'
	Figure 41 - Geoelectric section and drilling results near Campbell, Calif.
	Figure 42 - Apparent resistivity profile and geologic interpretation over buried channel, near Salisbury, Md
	Figure 43 - Buried stream channel near Bremerhaven, West Germany, mapped from electric sounding (after Hallenbach, 1953)
	Figure 44 - Map of apparent resistivity in the Bad-Krozingen geothermal area, Germany
	Figure 45 - Map of apparent resistivity in geothermal areas in New Zealand
	Figure 46 - Map of apparent resistivity in White Sands area, New Mexico, for electrode spacing AB/2 = 1,000 feet
	Figure 47 - Map of White Sands area, New Mexico, showing isobaths of the lower surface of fresh-water aquifer
	Figure 48 - Examples of Schlumberger sounding curves obtained near Bowie, Ariz
	Figure 49 - Block diagram of Pohakuloa-Humuula area, Hawaii
	Figure 50 - Geoelectric section north of Bowie, Ariz.
	Figure 51 - Examples of Schlumberger sounding curves obtained in the White Sands area, New Mexico
	Figure 52 - Apparent resistivity and apparent chargeability IP sounding curves for a four-layer model
	Figure 53 - Geoelectric Section, VES and IP sounding curves of alluvial deposits in Crimea
	Figure 54 - Schematic ray-path diagram for seismic energy generated at source S and picked up at geophone G
	Figure 55 - Huygens' construction for a head wave generated at the V1-V2 interface
	Figure 56 - Seismic wave fronts and traveltime plot for an idealized horizontally layered model
	Figure 57 - Schematic traveltime curves for idealized nonhomogenous geologic models
	Figure 58 - Comparison of 97 seismic refraction depth determinations versus drill-hole depths at the same localities
	Figure 59 - Seismic cross section, drill-hole data, and traveltime curves for a buried Tertiary stream channel in northern Nevada County, Calif.
	Figure 60 - Structure contours on the buried bedrock surface of the Passaic River Valley, northern New Jersey, based on seismic refraction and drill-hole measurements
	Figure 61 - Seismic cross section of the Jordan Valley east of Great Salt Lake, Utah
	Figure 62 - Distribution of observed compressional wave velocities in unsaturated sediments of the ancestral Miami River Valley, Ohio
	Figure 63 - Plot of observed porosity versus compressional wave velocity for unconsolidated sediments
	Figure 64 - Gravitational attraction at point P due to buried mass dm
	Figure 65 - A: Observed gravity profile for a buried sphere in a homogeneous rigid nonrotating Earth.  B: Sources of variation present in gravitational measurements made in the search for a buried sphere in a schematic, but real, Earth model
	Figure 66 - Bouguer gravity profiles across a low ridge based on six different densities employed in calculating the Bouguer correction
	Figure 67 - Schematic models and associated Bouguer gravity anomalies for idealized geologic bodies
	Figure 68 - Plot of observed compressional wave velocities versus density for sediments and sedimentary rocks
	Figure 69 - A: Complete Bouguer-gravity map of a buried pre-glacial channel of the Connecticut River.  B: Complete Bouguer-gravity map of part of San Georgino Pass, Calif.
	Figure 70 - A: Distribution of outcrops and structure contours on the buried bedrock surface, Perris Valley, Calif.  B: Bouguer-gravity map of Perris Valley, Calif.
	Figure 71 - Profiles of observed Bouguer gravity, residual gravity, and calculated porosity for Perris Valley, Calif.
	Figure 72 - In situ density log determined with a borehole gravity meter; drill hole UCe-18, Hot Creek Valley, Nev.
	Figure 73 - Plots of gravity values versus depth to the water table for aquifers having a porosity of 33 percent and specific retentions of 0 percent and 20 percent, respectively
	Figure 74 - Aeromagnetic profile at 230m above Gem Valley, Idaho
	Figure 75 - Aeromagnetic map of Gem Valley and adjoining areas, Idaho
	Figure 76 - Gravity and aeromagnetic profiles across Cenozoic basin in Antelope Valley, Calif.
Document Text Contents
Page 1

Techniques of Water-Resources Investigations
of the United States Geological Survey




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

Click here to return to USGS Publications

Page 61

........ ........... ........... ........... ........... ........... ........... ........... ........... ......... ......... ........ ......





1111 lo-100nm 0 1 2 3Km

........... 0 12 3 Miles...........
;i;;i;i;;;;100-200 t2m

v/h 200-350~ m


Figure 43.-Buried skeom channel near Bremerhoven, West Germany, mopped from elec­
trical sounding (after Hallenbach, 1953). Resistivities of more than- 200 ohm-m were
interpreted to be within the buried channel. Reproduced with permission of “Geophysical

Mapping the Water Table

Unlike the mapping of the fresh-salt water
interface, the determination of the depth to
the water table is generally a more difficult
problem. Deppermann and Homilius (1965)
investigated the geoel&tric conditions where
the water table can be detected on an elec­
trical sounding curve. Wherever the water
table is overlain and underlain by several
layers of different resistivities, its detection
on a sounding curve may be virtually im­
possible. Under favorable conditions the wa­

ter table can (bedetect4 on a sounding curve
aa a conductive layer.

,On the island of Hawaii, Zohdy and Jack-
son (1969) made several deep electrical
soundings to determine the depth to low-
resistivity layers that may relpresent basaltic
lava saturated wih water. !Phey concluded
that the minimum depth to such a layer is
of the order of 900 m (3,000 feet) (the sur­
vey was made at an average elevation of
about 1,900 m (6,200 feet) above sea level)..
A block diagram based on the interpretation
of electrical soundings in the Pohakuloa

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