U.S. Department of the Interior

U.S. Geological Survey

Analysis of Borehole-Radar Reflection 

Logs from Selected HC Boreholes at 

the Project Shoal Area, Churchill 

County, Nevada

By John W. Lane, Jr., Peter K. Joesten, Greg Pohll, and Todd Mihevic

Water-Resources Investigations Report 01-4014

Prepared in cooperation with the U.S. Department of Energy

Storrs, Connecticut

2001
U.S. DEPARTMENT OF THE INTERIOR

GALE A. NORTON, Secretary

U.S. GEOLOGICAL SURVEY

Charles G. Groat, Director

The use of firm, trade, and brand names in this report is for identification purposes 

only and does not constitute endorsement by the U.S. Government.

For additional information write to: 

Branch Chief

U.S. Geological Survey, Office of Ground Water

Branch of Geophysical Applications & Support

11 Sherman Place, U-5015

Storrs Mansfield, CT 06269

http://water.usgs.gov/ogw/bgas

Copies of this report can be purchased from:

U.S. Geological Survey

Branch of Information Services

Box 25286

Denver, CO 80225

http://www.usgs.gov
CONTENTS

Abstract ...................................................................................................................................... 1

Introduction .................................................................................................................................. 1

 Purpose and Scope .................................................................................................................... 2

 Description of the Study Area ....................................................................................................... 2

Data Collection and Analysis ........................................................................................................... 2

 Borehole-Radar Reflection Method ................................................................................................ 2

 Data Processing .................................................................................................................. 5

 Data Analysis and Interpretation .............................................................................................. 5

 Estimation of Reflector Length ................................................................................................ 6

 Reflector Quality Scores: Reflector Continuity and Orientation Confidence .............................................. 7

Results of Borehole-Radar Reflection Logging at the Project Shoal Area ......................................................... 9

 Borehole HC-2 .......................................................................................................................... 9

 Borehole HC-5 ......................................................................................................................... 9

 Borehole HC-6 ...................................................................................................................... 12

 Borehole HC-7 ...................................................................................................................... 14

 Borehole HC-8 ...................................................................................................................... 14

Summary and Conclusions .............................................................................................................. 18

References Cited .......................................................................................................................... 22

FIGURES

1. Map showing the location of the study area, general topography, and logged boreholes at the

 Project Shoal Area, Churchill County, Nevada ........................................................................... 3

2. Conceptual diagram showing the transmitter and receiver antenna arrangement for borehole-radar

 reflection logging and the typical reflection patterns from planar and a point reflectors .............................. 4

3. Diagram showing how the orientation of a receiving loop antenna with respect to an impinging 

 transmitted electromagnetic wave affects the amplitude of the signal induced on the 

 receiving antenna................................................................................................................. 5

4. Screen capture showing the use of RADINTER software to interactively interpret borehole 

 radar reflection logs ............................................................................................................. 6

5. Diagram showing the effect of reflector orientation on reflection imaging ................................................ 8

6. Radar reflection logging in borehole HC-2, Project Shoal Area .............................................................. 10

7. Radar reflection logging in borehole HC-5, Project Shoal Area ............................................................. 11

8. Radar reflection logging in borehole HC-6, Project Shoal Area ............................................................. 13

9. Radar reflection logging in borehole HC-7, Project Shoal Area ............................................................. 15

10. Radar reflection logging in borehole HC-8, Project Shoal Area ............................................................. 17

11. Histogram showing the distribution of interpreted borehole-radar reflectors sorted by azimuth, 

 Project Shoal Area ............................................................................................................. 19

12. Histogram showing the distribution of interpreted borehole-radar reflectors sorted by dip,

 Project Shoal Area ............................................................................................................. 19

13. Histogram showing the distribution of interpreted borehole-radar reflectors sorted by the continuity 

 of the reflectors, Project Shoal Area ........................................................................................ 20

14. Histogram showing the distribution of interpreted borehole-radar reflectors sorted by orientation 

 confidence, Project Shoal Area .............................................................................................. 20

15. Lower hemisphere equal-area stereo-net showing poles of all interpreted radar reflectors, weighted 

 by reflector length and combined reflector quality, Project Shoal Area ................................................ 21

Contents III
TABLES

1. Radar reflection logging parameters, Shoal Area, Churchill County, Nevada.................................................. 9 

2. Planar reflectors interpreted from 60-megahertz radar reflection log, borehole HC-2, Project Shoal Area .............. 12

3. Planar reflectors interpreted from 60-megahertz radar reflection log, borehole HC-5, Project Shoal Area .............. 12

4. Planar reflectors interpreted from 60-megahertz radar reflection log, borehole HC-6, Project Shoal Area ............... 14

5. Planar reflectors interpreted from 60-megahertz radar reflection log, borehole HC-7, Project Shoal Area .............. 16

6. Planar reflectors interpreted from 60-megahertz radar reflection log, borehole HC-8, Project Shoal Area .............. 16

CONVERSION FACTORS AND ABBREVIATIONS

 

 Other abbreviations used in this report:

 °, degrees

 MHz, megahertz

Multiply By To obtain

kilometer (km) 0.6214 mile

meter (m) 3.281 foot

IV Contents 
ABSTRACT

Single-hole borehole-radar reflection logs 

were collected and interpreted in support of a 

study to characterize ground-water flow and 

transport at the Project Shoal Area (PSA) in 

Churchill County, Nevada. Radar logging was 

conducted in six boreholes using 60-MHz 

omni-directional electric-dipole antennas and a 

60-MHz magnetic-dipole directional receiving 

antenna.

Radar data from five boreholes were 

interpreted to identify the location, orientation, 

estimated length, and spatial continuity of planar 

reflectors present in the logs. The overall quality 

of the radar data is marginal and ranges from 

very poor to good. Twenty-seven reflectors were 

interpreted from the directional radar reflection 

logs. Although the range of orientation 

interpreted for the reflectors is large, a significant 

number of reflectors strike northeast-southwest 

and east-west to slightly northwest-southeast. 

Reflectors are moderate to steeply dipping and 

reflector length ranged from less than 7 m to 

more than 133 m.

Qualitative scores were assigned to each 

reflector to provide a sense of the spatial 

continuity of the reflector and the characteristics 

of the field data relative to an ideal planar 

reflector (orientation score). The overall 

orientation scores are low, which reflects the 

general data quality, but also indicates that the 

properties of most reflectors depart from the ideal 

planar case. The low scores are consistent with 

reflections from fracture zones that contain 

numerous, closely spaced, sub-parallel fractures. 

Interpretation of borehole-radar directwave velocity and amplitude logs identified 

several characteristics of the logged boreholes: 

(1) low-velocity zones correlate with decreased 

direct-wave amplitude, indicating the presence of 

fracture zones; (2) direct-wave amplitude 

increases with depth in three of the boreholes, 

suggesting an increase in electrical resistivity 

with depth resulting from changes in mineral 

assemblage or from a decrease in the specific 

conductance of ground water; and (3) an increase 

in primary or secondary porosity and an 

associated change in mineral assemblage, or 

decrease in ground water specific conductance, 

was characterized in two of the boreholes below 

300 m. 

The results of the radar reflection logging 

indicate that even where data quality is marginal, 

borehole-radar reflection logging can provide 

useful information for ground-water 

characterization studies in fractured rock and 

insights into the nature and extent of fractures 

and fracture zones in and near boreholes.

INTRODUCTION

In October 1963, an underground nuclear test 

was conducted at the Project Shoal Area (PSA) in 

Churchill County, about 50 km southeast of Fallon, 

Nevada. The nuclear test was conducted as part of a 

research program designed to enhance the detection of 

Analysis of Borehole-Radar Reflection Logs From 

Selected HC Boreholes at the Project Shoal Area, 

Churchill County, Nevada

By John W. Lane Jr., Peter K. Joesten, Greg Pohll, and Todd Mihevic

ABSTRACT 1
underground nuclear tests in seismically active areas 

(Pohll and others, 1998). Because underground 

nuclear tests deposit radioactive materials in the 

subsurface, there is a potential for radioactive 

materials to directly contact and contaminate ground 

water. At the PSA, the U.S. Department of Energy is 

conducting characterization studies of ground-water 

contamination to establish contaminant boundaries to 

protect human health and the environment (Pohll and 

others, 1998). 

In support of the ground-water studies, a 

cooperative project was conducted by the U.S. 

Department of Energy and the U.S. Geological 

Survey under Interagency Agreement DE-A108-

96NV11967. Borehole-radar reflection logging was 

conducted in six boreholes in the PSA to identify 

large fractures and fractures zones in and near the 

boreholes. The radar logs were analyzed and 

interpreted by the U.S. Geological Survey to identify 

planar and point reflectors near the boreholes, 

estimate the orientation of reflectors, determine the 

projection depth of the reflectors relative to the 

boreholes, and identify characteristics of the reflection 

logs that could provide information about the nature 

and extent of fractures and fracture zones in and near 

the boreholes. 

Purpose and Scope

This report presents results of the analysis and 

interpretation of borehole-radar reflection data 

acquired in six boreholes at the PSA. The analysis of 

the radar data included determination of the location 

and orientation of planar and point reflectors, 

approximation of the length of planar reflectors, and 

qualitative estimation of the relative continuity and 

characteristics of reflectors in the field data relative to 

an ideal planar reflector. Results of the analysis are 

presented in tabular form, stereo plots, and 

histograms. In addition, the relative arrival time and 

amplitude of the direct wave traveling between the 

radar transmitter and receiver was analyzed. Results 

of the direct-wave analysis are provided in graphical 

form as radar velocity and amplitude logs.

Description of the Study Area

The PSA is in Churchill County, Nevada, 

about 50 km southeast of Fallon, Nevada (fig. 1). The 

regional ground-water hydrology is described by 

Cohen and Everett (1963) and Glancy and Katzer 

(1975). The University of Nevada (1965) reported 

results of geologic and topographic mapping, drilling 

operations, geophysical surveys, hydrologic testing, 

and geologic core analysis. Investigations have been 

undertaken to characterize the hydrogeology of the 

PSA and the effects of the nuclear test. These studies 

were tabulated and summarized by Pohll and others 

(1998). 

As described in Pohll and others (1998), the 

PSA is in the Sand Springs Range, a north-south 

trending range in Nevada’s Great Basin. The Sand 

Springs Range is bounded by near-vertical, northeastand northwest-trending faults. Within the range, an 

intrusive granitic body of Cretaceous age is 

surrounded by metamorphosed Paleozoic and 

Mesozoic marine sediments. Intermittent faulting is 

present in the center of the Sand Springs Range as 

high- to moderate-angle, northeast- and northwesttrending faults. The Project Shoal test was conducted 

in the granite uplift of the Sand Springs Range. Near 

the site, ground water is present in the fractured 

granite about 300 m below land surface. 

DATA COLLECTION AND ANALYSIS

Borehole-Radar Reflection Method

Borehole-radar reflection methods can 

provide information about the extent and orientation 

of fracture zones intersected by a borehole and 

fracture zones outside of the borehole that are not 

penetrated by drilling. This provides information 

about the rocks outside the borehole that would not be 

provided by tools that characterize only the interior of 

a borehole. The ability of the method to ”see” beyond 

the borehole can potentially provide valuable insight 

about the network of fractures in and near boreholes.

Borehole-radar systems and methods have 

been developed in the United States (Rubin and 

others, 1978; Wright and Watts, 1982) and in Sweden 

(Nilsson, 1983; Olsson and others, 1988). Single-hole 

radar reflection methods (using omni-directional and 

directional receiver antennas) have been used to 

detect and map fractures and fracture zones at 

proposed high-level nuclear waste sites (Bradley and 

Wright, 1987; Olsson and others, 1988, 1992a, 1992b; 

Sandberg and others, 1991; Holloway and others, 

1992; Stevens and others, 1995) and are increasingly 

2 Analysis of Borehole-Radar Reflection Logs from Selected HC Boreholes at the Project Shoal Area, Churchill County, Nevada 
utilized for ground-water investigations (Haeni and 

others, 1993; Gaylor and others, 1994; Lane and 

others, 1994; Hansen and Lane, 1995). The ABEM 

RAMAC borehole-radar system used for this study 

was developed by the Swedish Geological Survey to 

investigate potential high-level nuclear waste disposal 

sites. 

Borehole-radar reflection logging is 

conducted by connecting a radar transmitter and 

receiver together as a logging tool (fig. 2). The 

transmitter and receiver are vertically oriented in a 

single borehole, and separated by a fixed distance. 

A high-frequency electromagnetic (EM) pulse is 

generated by the transmitting antenna and propagates 

radially into the surrounding material. Some of the 

energy is reflected when it encounters changes in the 

physical properties of the rock surrounding the 

borehole, such as at fractures or point-like 

discontinuities. Transmitted (direct-wave) and 

reflected energy arriving at the receiving antenna is 

recorded as a function of time (fig. 2). 

Reflection logging can be conducted with 

omni-directional or directional receiving antennas. 

The transmitter and the receiver antennas are moved 

down a single hole using a computer-controlled 

winch, and measurements are collected at discrete, 

regular intervals. The transmitter-receiver antenna 

separation can range from 1 to 15 m depending on the 

radar system, selection of antenna frequency and 

design, and electrical resistivity of the rock. The 

borehole measurement interval usually ranges from 

about 0.1 to 1.0 m. Omni-directional (electric-dipole) 

antennas provide information on the dip and depth of 

a reflector with respect to the borehole, but do not 

provide information on the orientation (strike) of a 

reflector. Directional receiving antennas can provide 

N

EXPLANATION

39

o 12' 29.80"

39

o 11' 30.18"

118

o 23' 33.11" 118o 22' 5.43"

Borehole

0 500 1000 1500 feet

0 250 500 m

Unimproved road

Contour interval = 50 m

(elevation in meters MSL)

Location of Project

Shoal Area in Nevada

118

o 23' 0"

39

o 12' 0"

Figure 1. Location of the study area, general topography, and logged boreholes at the Project Shoal Area, 

Churchill County, Nevada.

DATA COLLECTION AND ANALYSIS 3
information on the orientation of reflectors. The 

directional receiver used for this study is a magneticdipole type described by Falk (1992). Although the 

directional receiver can determine the orientation of 

planar reflectors and the azimuths to point reflectors, 

the antenna is less sensitive than the electric-dipole 

antenna. The radial penetration of the directional 

antenna used for this study is typically 50 to 

70 percent that of the penetration achieved by the 

omni-directional antenna.

The basic principles of single-hole reflection 

surveying and the typical reflection patterns for planar 

and point reflectors, such as fractures or voids, are 

illustrated in figure 2. The first signal to arrive at the 

receiver is the direct wave, which propagates from the 

transmitter, through the rock, to the receiver. Due to 

the small diameter of most boreholes relative to the 

EM wavelengths used for radar reflection logging, 

propagation of energy along the borehole is small and 

limited to very high frequencies. As the transmitter 

and receiver antenna pair approach and pass a point 

scatterer, an approximately hyperbolic reflection is 

obtained with the apex of the hyperbola at the point 

closest to the borehole (fig. 2). As the transmitter and 

receiver antennas approach a planar reflector that 

intersects the borehole, the reflection travel time 

decreases until it merges with the direct arrival. As 

the transmitter and receiver pass through the 

intersection location of the reflector, no reflections are 

obtained and a delay of the arrival time of the direct 

wave can occur, if, for example, the reflector is a 

water-filled fracture or fracture zone. As the 

transmitter and receiver move past the reflector 

intersection point, the reflection travel time increases, 

resulting in a two-limbed or chevron-shaped reflection 

pattern for a reflector that intersects the borehole 

(fig. 2). The reflection pattern for reflectors that do 

not intersect the borehole is discontinuous and 

displays only the upper (up-dip) or lower (down-dip) 

limb (fig. 2).

The EM-wave propagation velocity is 

required to accurately interpret the dip of planar 

reflectors and the radial distance to point reflectors. 

The EM velocity for different rock types can be 

roughly estimated from tabulations found in the 

literature (Cook, 1975), by vertical radar profiling 

(VRP) tests, and by analysis of the shape of the 

reflections from point reflectors. VRP testing is 

performed by fixing the transmitter location while 

making measurements as the receiver is moved away 

from the transmitter in fixed increments. The slope of 

the best-fit line of the transmitter-receiver distance 

plotted against the arrival time yields the average 

velocity along the borehole.

Variations in the arrival time and amplitude 

of the direct wave provide information about the 

Reflected 

energy

Depth

Time

Direct-wave

Reflection from

planar feature

Receiver

Transmitter

Point

 reflector

Fracture Transmitted 

energy

Reflection from

point object

Reflector from 

planar fracture not 

intercepting the 

borehole

Fracture

Figure 2. Transmitter and receiver antenna arrangement for borehole-radar reflection logging and the typical 

reflection patterns from planar and point reflectors.

4 Analysis of Borehole-Radar Reflection Logs from Selected HC Boreholes at the Project Shoal Area, Churchill County, Nevada 
range of velocity and attenuation differences of the 

material surrounding the borehole. In resistive, 

saturated rocks, a delayed arrival of the direct wave 

(decreased velocity) coupled with a decreased pulse 

amplitude can indicate an increase in porosity due to 

fracturing; the high dielectric permittivity of water 

reduces EM-wave velocity.

Data Processing

For this study, signal processing of boreholeradar data was limited to (1) removal of the directcurrent (DC) offset and (2) band-pass filtering 

(Yilmaz, 1987). The DC offset is caused by the 

analog-to-digital sampling electronics, which induce a 

drift in the signal level with time. The DC offset is 

removed by averaging the DC level of the first few 

samples of each trace before the onset of the direct 

arrival, and subtracting this average from the rest of 

the samples. Band-pass filtering is used to remove 

low- and high-frequency random and system noise 

and other sources of noise, such as ringing induced by 

the impedance mismatch of the antennas with the 

borehole. 

Data Analysis and Interpretation

Interpretation of the strike of a planar feature 

or the azimuth to a point reflector is performed in a 

manner analogous to certain methods of radiodirection finding. Using a loop antenna, it is possible

to locate the radial direction to a transmitter by 

rotating the loop and measuring the signal induced on 

the receiving antenna. The magnetic component of the 

electromagnetic wave induces an electric current in 

the loop. The electromotive force in the loop is a 

function of the magnetic flux through the loop. 

Therefore, the signal induced by a plane wave is a 

function of the component of the variable magnetic 

field passing through the antenna loop (fig. 3). 

Figure 3. Effect of the orientation of a receiving loop antenna, with respect to an impinging transmitted 

electromagnetic wave, on the amplitude of the signal induced on the receiving antenna: (A) antenna loop 

parallel to incident electric field receives the maximum signal amplitude, (B) antenna loop perpendicular to 

incident electric field receives minimal signal amplitude.

(A) (B)

Magnetic 

field Magnetic 

field

Electric 

field

Electric 

field

Receiving 

loop 

antenna

Receiving 

loop 

antenna

DATA COLLECTION AND ANALYSIS 5
Maximum signal is induced on the antenna when the 

plane of the loop is parallel to the radial direction to 

the transmitter. The location of the transmitter is 

found by determining the radial direction to the 

transmitter from at least two different locations.

For radar reflection logging, locating the 

direction to a reflection source is similar to the radiodirection finding problem of locating the direction to a 

transmitter. In a borehole, however, the direction of 

movement is limited to the borehole axis, and 

physical rotation of the antenna is not desirable due to 

the power demands of a mechanical apparatus. 

Therefore, specially designed directional antennas are 

required to determine the strike, dip, and intersection 

location of planar reflectors, and the azimuth, depth, 

and radial distance of point reflectors. The directional 

receiving antenna used for this study is a magnetic 

dipole tool containing four orthogonal, resistivelyloaded, transmission line antennas, which have the 

same directional radiation properties described for the 

loop antennas, but with improved signal 

characteristics (Falk, 1992). The antenna contains a 

three-component magnetometer and a plunge sensor 

to determine the orientation of the receiver for each 

measurement. The four antennas allow the sampling 

of the spatial components of the reflected 

electromagnetic waves, without resorting to the 

physical rotation of the antennas. 

For this study, the commercial software 

RADINTER was used to interpret the radar reflection 

logs. RADINTER is an interactive program that 

allows the user to interpret the projected intersection 

depth, dip, and strike of planar reflectors and the 

azimuth to point reflectors. This is done using 

information on the logging measurement parameters, 

including distance between the transmitter and 

receiver, measurement start location, measurement 

interval, sampling frequency, and average EM

propagation velocity (fig. 4). A complete description 

of the procedures used to interpret the directional data 

can be found in Falk (1992). Note that the projected 

intersection depth is relative to the line formed by the 

axis of the borehole. Therefore, the projected 

intersection depth can be below the drilled depth of 

the borehole, in the cased portion of a borehole, or can 

be negative, which indicates the reflector projects to 

the borehole axis above the ground surface. 

Estimation of Reflector Length

Simple geometric concepts can be used to 

analyze the planar reflectors observed in radar 

reflection logs. The simplifications ignore important 

details such as Fresnel zone and edge effects needed 

Figure 4. Screen capture showing the use of RADINTER software to interactively interpret borehole-radar reflection 

logs.

6 Analysis of Borehole-Radar Reflection Logs from Selected HC Boreholes at the Project Shoal Area, Churchill County, Nevada 
for a more comprehensive analysis; nonetheless, using 

straight-ray approximations and right-angle 

trigonometry, useful information about the nature and 

extent of planar reflectors can be extracted from radar 

reflection logs. For a thorough discussion of 

reflection physics, see Yilmaz (1987). 

For planar reflectors, the part of the reflector 

imaged by the logging process is the component 

parallel to the borehole. Thus, the imaging process is 

biased by the orientation of the reflector relative to the 

borehole. For example, the effect of orientation bias 

on reflectors oriented parallel and perpendicular to the 

borehole is shown in figure 5. A reflector oriented at a 

large angle to the borehole reflects EM waves from 

nearly the same spot as the radar tool is moved along 

the borehole, whereas for reflectors parallel to the 

borehole, the imaged spot moves as the radar tool 

moves (fig. 5). The orientation bias also affects 

estimates of the location and radial distance to a 

reflection point; this is similar to the classic migration 

problem of reflection seismology (Yilmaz, 1987). 

Using the geometry shown in figure 5, a 

reasonable approximation of the radial distance to a 

point on a reflector is given by

 Dcor = Dest cos(α) (1)

where

 Dcor is the corrected radial distance from the

 borehole, 

 Dest is the estimated distance to reflection

 point, accounting for fixed transmitter-

 receiver offset, and

 α is the angle of planar reflector to the

 borehole.

Using this simple radial distance correction, 

the procedure for calculating the length of a limb of a 

planar reflector is to (1) use RADINTER to determine 

the angle of the reflector relative to the borehole; (2) 

estimate the maximum radial extent of the limb from 

the reflection record; and (3) correct this distance 

estimate using equation (1). An estimate of the length 

of the reflector parallel to the borehole, assuming that 

the reflector projects close to or intersects the 

borehole, is given by

 Lest = Dcor sin(α) (2)

where Lest is the estimated length of imaged reflector.

Reflector Quality Scores: Reflector 

Continuity and Orientation Confidence

The ideal models and simple geometries used 

to describe theoretical reflection properties often fail 

to predict real earth reflection characteristics. For 

example, the ideal planar reflector describes a smooth 

surface with constant or slowly changing differences 

in physical properties. In contrast, fracture zones can 

cross lithologic boundaries; be non-planar; be locally 

discontinuous; and have abrupt changes in the 

number, length, and orientation of fractures in the 

zone. Also, the radar antennas used for this study 

couple with and are modified by the medium 

surrounding the antennas. Therefore, real antenna 

response can and does depart from ideal predicted 

response. 

Because of the differences between ideal and 

real behavior, a qualitative system of scoring is used 

to provide a sense of the quality of the data and the 

confidence in a given interpretation relative to an 

idealized case. For this study, two scores, ranging 

from 1 (best) to 5 (worst) are assigned to each 

reflector for the following categories: (1) reflector 

continuity and (2) orientation confidence. 

The reflector continuity score provides a 

sense of the spatial persistence of a reflector across 

the radar reflection log. A score of 1 is assigned to 

high-amplitude reflectors that originate at or close to 

the direct wave and are clearly visible with little or no 

amplitude variations. This type of reflector closely 

approximates the ideal planar reflector. A reflector 

continuity score of 3 is assigned to reflectors that 

show some discontinuity and amplitude variation but 

can be followed relatively easily across the radar 

reflection log. This type of reflector is consistent with 

a locally discontinuous fracture or fracture zone. A 

reflector continuity score of 5 is assigned to reflectors 

that are observed in small segments that are isolated 

and (or) extremely difficult to follow or trace across 

the radar reflection record. This type of reflector is 

consistent with isolated, spatially discontinuous 

fractures and inhomogeneities. 

The orientation confidence score provides an 

indication of the azimuthal (directional) behavior of 

the reflector relative to the behavior predicted for 

ideal planar reflectors. The score is also a measure of 

the confidence of the interpretation. A score of 1 is 

assigned to reflectors that behave as ideal planar 

reflectors. A score of 3 is assigned to reflectors that 

DATA COLLECTION AND ANALYSIS 7
Figure 5. Effect of reflector orientation on reflection imaging. 

8 Analysis of Borehole-Radar Reflection Logs from Selected HC Boreholes at the Project Shoal Area, Churchill County, Nevada 

α

Borehole

Transmitter

Receiver

Fracture planes

Radial

reflection

distance
are partially obscured by other reflectors or where 

some interference effects are observed but a 

reasonable interpretation is still possible. These 

reflectors are consistent with locally discontinuous 

fractures or fracture zones. A score of 5 is assigned to 

reflectors that are degraded by severe interference, are 

difficult to observe at important angles, or are located 

where the electric-dipole component is missing or 

obscured. This type of reflector is consistent with 

chaotic fracture zones or faint reflectors in parts of the 

reflection record having low signal strength.

RESULTS OF BOREHOLE-RADAR 

REFLECTION LOGGING AT THE 

PROJECT SHOAL AREA

Omni-directional and directional-radar 

reflection logging was conducted using 60-MHz 

transmitting and receiving antennas in boreholes 

HC-1, HC-2, HC-5, HC-6, HC-7, and HC-8 at the 

Project Shoal Area, Churchill County, Nevada 

(fig. 1). Field logging parameters are listed in table 1. 

Figures 6 to 10 show (1) processed borehole-radar 

reflection logs; (2) lower-hemisphere equal-area 

stereo-nets showing the poles of the radar reflectors 

weighted by reflector length and combined quality 

score; and (3) logs showing the results of direct-wave 

velocity and amplitude analysis. Tables 2-6 give the 

location, orientation, length, and quality scores for the 

interpreted reflectors in each borehole. 

The quality of the borehole-radar data ranged 

from very poor to good, with most data in the poor to 

fair range. Assuming that the radar equipment was 

functioning properly, the range in data quality can be 

attributed to the relatively low resistivity of the rocks 

underlying the PSA. As electrical resistivity 

decreases, attenuation of EM waves increases. 

Therefore, the radial penetration of the radar pulse 

into the rock is attenuated. In addition, as electrical 

resistivity decreases, a threshold is reached at which 

diffusive behavior dominates, and EM-wave 

propagation is no longer possible. The quality of the 

radar data collected from borehole HC-1 is so poor 

that it was uninterpretable; by contrast, the quality of 

the data from HC-6 and HC-7 was sufficient to map 

reflectors more than 10 m from the borehole.

Borehole HC-2

Radar reflection logging in borehole HC-2 

was limited to omni-directional logging (table 1). 

Data quality was good (fig. 6A), with radial 

penetration exceeding 15 m. A total of 8 reflectors 

were interpreted from the reflection log (table 2). The 

estimated length of the reflectors imaged in HC-2 

ranges from less than 3 m to more than 40 m. 

Interpreted dips range from about 15 to 80°, with a 

median dip of 60°. The direct-wave logs indicate the 

presence of low-velocity zones at depths of about 300 

and 335 m (fig. 6B and 6C). Direct-wave amplitude 

and radial penetration increase below about 330 m, 

indicating that the electrical resistivity of the rocks 

below this depth increases.

Borehole HC-5

Radar reflection logging in borehole HC-5 

included omni-directional and directional logging 

(table 1). The quality of the omni-directional and 

directional radar data was poor (fig. 7A), with few 

Borehole 

number

Starting 

depth 

(meters)

Stopping 

depth 

(meters)

Step 

(meters)

Sampling 

frequency 

(megahertz)

Directional 

data 

collected

Omnidirectional 

data 

collected

Comments

HC-1 339.25 400.00 0.25 1605.73 -- x uninterpretable

HC-2 294.00 367.00 0.50 719.43 -- x -

HC-5 390.00 592.00 0.50 917.60 x x -

HC-6 229.00 360.00 0.50 1376.36 x x -

HC-7 139.00 366.50 0.50 1310.82 x x -

HC-8 394.00 742.00 0.50 917.60 x x -

Table 1. Radar reflection logging parameters, Project Shoal Area, Churchill County, Nevada 

[x, data collected; --, no data collected; -, none]

RESULTS OF BOREHOLE-RADAR REFLECTION LOGGING AT THE PROJECT SHOAL AREA 9
Figure 6. Radar reflection logging in borehole HC-2, Project Shoal Area, Churchill County, Nevada: (A) 60-

megahertz electric-dipole omni-directional radar reflection log, (B) direct-wave amplitude log, (C) direct-wave 

radar velocity log.

290

300

310

320

330

340

350

360

370

0 10000 20000 30000 40000

PEAK-TO-PEAK AMPLITUDE, IN 

MICROVOLTS

DEPTH BELOW TOP OF CASING, IN METERS

290

300

310

320

330

340

350

360

370

0.09 0.10 0.11 0.12 0.13 0.14 0.15

RADAR PROPAGATION VELOCITY,

IN METERS PER NANOSECOND

DEPTH BELOW TOP OF CASING, IN METERS

0.0 0.1 0.2

TWO-WAY TRAVEL TIME, IN MICROSECONDS

0 5 10 15

RADIAL DISTANCE, IN METERS

300

320

340

360

DEPT

H BELOW

TOP OF C

A

SIN

G, IN

METER

S

AMPLITUDE,

IN

MICROVOLTS

10000

5000

2500

1000

-10000

-5000

-2500

-1000

-500

-250

-100

0

100

250

500

(A)

(B) (C)

10 Analysis of Borehole-Radar Reflection Logs from Selected HC Boreholes at the Project Shoal Area, Churchill County, Nevada 
450

500

550

600

650

700

750

0 10000 20000 30000 40000

PEAK-TO-PEAK AMPLITUDE, IN 

MICROVOLTS

DEPTH BELOW TOP OF CASING, IN METERS

0 10000 20000 30000 40000

Figure 7. Radar reflection logging in borehole HC-5, Project Shoal Area, Churchill County, Nevada: (A) 60-

megahertz magnetic-dipole directional radar reflection log, (B) lower hemisphere equal-area stereo-net showing 

poles of interpreted reflectors, (C) direct-wave amplitude log, (D) direct-wave radar velocity log.

450

500

550

600

650

700

750

0.09 0.10 0.11 0.12 0.13 0.14 0.15

RADAR PROPAGATION VELOCITY,

IN METERS PER NANOSECOND

DEPTH BELOW TOP OF CASING, IN METERS

0.0 0.1 0.2

TWO-WAY TRAVEL TIME, IN MICROSECONDS

0 5 1 0 1 5

RADIAL DISTANCE, IN METERS

5 00

6 00

7 00

DEPTH, IN METERS BELOW TOP OF C

ASING

AMPLITUDE,

IN

MICROVOLTS

10000

5000

2500

1000

-10000

-5000

-2500

-1000

-500

-250

-100

0

100

250

500

N

poor to very poor

good to very good

fair

(C) (D)

(A) (B)

RESULTS OF BOREHOLE-RADAR REFLECTION LOGGING AT THE PROJECT SHOAL AREA 11
interpretable reflectors. Three reflectors were 

interpreted from the directional reflection log 

(table 3). Two reflectors strike west to southwest, 

dipping between 65 and 70°, one reflector strikes 10° 

east of north with a dip of 46°. These data are plotted 

on a pole-plane stereonet (fig. 7B). Each reflector is 

symbolized as a pole to the reflector plane, projected 

onto a lower-hemisphere, equal-area stereonet. The 

estimated length of the reflectors imaged in HC-5 

ranges from less than 7 m to more than 40 m. The 

direct-wave logs indicate the presence of several 

minor low-velocity zones at depths of about 500, 520, 

570, and 620 m. Direct-wave amplitudes generally 

increase with depth except near the low-velocity 

zones (figs. 7C and 7D). 

Borehole HC-6

Radar reflection logging in borehole HC-6 

included omni-directional and directional logging 

(table 1). The quality of the omni-directional and 

directional radar data was fair to good (fig. 8A). Five 

reflectors were interpreted from the directional 

reflection log (table 4). One reflector strikes to the 

northwest with a dip of 83°. Two reflectors strike 

southwest dipping at 71 and 80°, and two reflectors 

strike southeast with dips of 63 and 73°, respectively 

(fig. 8B). The median dip of the interpreted reflectors 

is 73°. The estimated length of the reflectors imaged 

in HC-6 ranges from less than 15 m to more than 140 

m; the median reflector length is 37 m. The directwave logs indicate the presence of low-velocity zones 

above 100 m and below 300 m. An isolated lowvelocity zone occurs at about 165 m. Direct-wave 

amplitudes generally increase with depth. The lowest 

direct-wave amplitudes occur above 100 m; 

amplitudes are fairly constant from 100 to 300 m 

except near the low velocity zone at 165 m (figs. 8C 

and 8D). It is interesting to note that direct-wave 

amplitudes increase below 300 m, whereas directwave velocities decrease over the same interval. This 

suggests that an increase in primary or secondary 

Depth from land 

surface 

(meters)

Dip 

(degrees)

Reflector continuity 

(1 = very good,

5 = very poor)

Estimated length of 

reflector 

(meters)

Comments

284.5 78 2 42.0 lower limb

299.5 62 4 24.0 lower limb

312.5 61 3 18.7 lower limb

318.5 52 4 8.7 lower limb

332.5 52 1 19.7 lower limb

333.2 15 3 2.6 lower limb

340.5 60 4 16.7 lower limb

354.4 60 5 8.7 lower limb

Table 2. Planar reflectors interpreted from 60-megahertz radar reflection log, borehole HC-2, Project Shoal Area, 

Churchill County, Nevada

Depth from 

land surface 

(meters)

Strike 

(degrees)

Dip 

(degrees)

Reflector 

continuity 

(1=very good, 

5=very poor)

Orientation 

confidence 

(1=very good, 

5=very poor)

Estimated 

length of 

reflector 

(meters)

Comments

448.1 260 65 4 4 41.5 upper limb

464.2 230 70 4 4 21.0 upper limb

482.7 10 46 3 5 6.6 lower limb

Table 3. Planar reflectors interpreted from 60-megahertz radar reflection log, borehole HC-5, Project Shoal Area, 

Churchill County, Nevada

12 Analysis of Borehole-Radar Reflection Logs from Selected HC Boreholes at the Project Shoal Area, Churchill County, Nevada 
Figure 8. Radar reflection logging in borehole HC-6, Project Shoal Area, Churchill County, Nevada: (A) 60-

megahertz magnetic-dipole directional radar reflection log, (B) lower hemisphere equal-area stereo-net showing 

poles of interpreted reflectors, (C) direct-wave amplitude log, (D) direct-wave radar velocity log.

0

50

100

150

200

250

300

350

400

0 10000 20000 30000 40000

PEAK-TO-PEAK AMPLITUDE, IN 

MICROVOLTS

DEPTH BELOW TOP OF CASING, IN METERS

0

50

100

150

200

250

300

350

400

0.09 0.10 0.11 0.12 0.13 0.14 0.15

RADAR PROPAGATION VELOCITY,

IN METERS PER NANOSECOND

DEPTH BELOW TOP OF CASING, IN METERS

0.0 0.1 0.2

TWO-WAY TRAVEL TIME, IN MICROSECONDS

0 5 10 15

RADIAL DISTANCE, IN METERS

100

200

300

DEPTH, IN METERS BELOW TOP OF C

ASING

AMPLITUDE,

IN

MICROVOLTS

10000

5000

2500

1000

-10000

-5000

-2500

-1000

-500

-250

-100

0

100

250

500

N

poor to very poor

good to very good

fair

(C) (D)

(A) (B)

RESULTS OF BOREHOLE-RADAR REFLECTION LOGGING AT THE PROJECT SHOAL AREA 13
porosity associated with a decrease in specific 

conductance of the ground water and (or) a change in 

mineral assemblage, is taking place in the rocks below 

300 m. 

Borehole HC-7

Radar reflection logging in borehole HC-7 

included omni-directional and directional logging 

(table 1). The quality of the omni-directional and 

directional radar data was fair to good (fig. 9A). 

Fourteen reflectors were interpreted from the 

directional reflection log (table 5). The reflectors are 

clustered in three groups: (1) a northwest-southeast 

striking set with dips ranging from 73 to 84°; (2) an 

east-west striking set with dips ranging from 80 to 

87°; and (3) a northeast-southwest striking set with 

dips ranging from 69 to 86° (fig. 9B). 

The estimated length of the reflectors imaged 

in HC-7 ranges from less than 18 to more than 130 m; 

the median reflector length is 50 m. The direct-wave 

amplitude logs from HC-7 are remarkably similar to 

the logs from HC-6, when shifted upward 50 m. The 

direct-wave logs indicate that a continuous structure 

or structures could connect boreholes HC-6 and HC-7. 

The lowest velocities are present above 120 m and 

below 300 m. Isolated low-velocity zones occur at 

about 185 and 225 m. As in HC-6, direct-wave 

amplitudes generally increase with depth. The lowest 

direct-wave amplitudes occur above 120 m; 

amplitudes are fairly constant from 120 to 270 m 

except near the low-velocity zone at 220 m (figs. 9C 

and 9D). As in HC-6, direct-wave amplitudes increase 

below 300 m over the same interval that direct-wave 

velocities decrease, indicating an increase in primary 

or secondary porosity coupled with a decrease in the 

specific conductance of ground water, and (or) a 

change in mineral assemblage.

Borehole HC-8

Radar reflection logging in borehole HC-8 

included omni-directional and directional logging 

(table 1). The quality of the omni-directional and 

directional radar data was fair (fig. 10A). Five 

reflectors were interpreted from the directional 

reflection log (table 6). All of the reflectors have 

strikes near north-south with dips ranging from 56 to 

71° with a median dip of 63° (fig. 10B). The 

estimated length of the reflectors imaged in HC-8 

ranges from less than 15 to about 28 m, the median 

reflector length is 19 m. The direct-wave logs indicate 

the presence of low-velocity zones near 630 and 

710 m. Additional isolated low-velocity zones occur 

at about 655 and 665 m. Direct-wave amplitudes are 

generally constant over the logged interval except for 

decreases near the low-velocity zones (figs. 10C and 

10D). 

Depth from 

land surface 

(meters)

Strike 

(degrees)

Dip 

(degrees)

Reflector 

continuity 

(1=very good, 

5=very poor)

Orientation 

confidence 

(1=very good, 

5=very poor)

Estimated 

length of 

reflector 

(meters)

Comments

218.0 310 83 3 4 147.8 lower limb

257.7 120 63 3 3 14.4 crossing

270.4 230 80 4 4 34.7 crossing

271.6 230 71 2 3 34.5 lower limb

332.7 100 73 4 3 40.0 upper limb

Table 4. Planar reflectors interpreted from 60-megahertz radar reflection log, borehole HC-6, Project Shoal Area, 

Churchill County, Nevada

14 Analysis of Borehole-Radar Reflection Logs from Selected HC Boreholes at the Project Shoal Area, Churchill County, Nevada 
0

50

100

150

200

250

300

350

400

0 10000 20000 30000 40000

PEAK-TO-PEAK AMPLITUDE, IN 

MICROVOLTS

DEPTH BELOW TOP OF CASING, IN METERS

0

50

100

150

200

250

300

350

400

0.07 0.08 0.09 0.10 0.11 0.12 0.13

RADAR PROPAGATION VELOCITY,

IN METERS PER NANOSECOND

DEPTH BELOW TOP OF CASING, IN METERS

0.0 0.1 0.2

TWO-WAY TRAVEL TIME, IN MICROSECONDS

0 5 10 15

RADIAL DISTANCE, IN METERS

100

200

300

DEPTH, IN METERS BELOWTOP OF C

ASING

AMPLITUDE,

IN

MICROVOLTS

10000

5000

2500

1000

-10000

-5000

-2500

-1000

-500

-250

-100

0

100

250

500

N

poor to very poor

good to very good

fair

(C) (D)

(A) (B)

Figure 9. Radar reflection logging in borehole HC-7, Project Shoal Area, Churchill County, Nevada: (A) 60-

megahertz magnetic-dipole directional radar reflection log, (B) lower hemisphere equal-area stereo-net showing 

poles of interpreted reflectors, (C) direct-wave amplitude log, (D) direct-wave radar velocity log.

RESULTS OF BOREHOLE-RADAR REFLECTION LOGGING AT THE PROJECT SHOAL AREA 15
Table 5. Planar reflectors interpreted from 60-megahertz radar reflection log, borehole HC-7, Project Shoal Area, 

Churchill County, Nevada

[ n/a, not applicable - represents dipole only]

Depth from 

land surface 

(meters)

Strike 

(degrees)

Dip 

(degrees)

Reflector 

continuity 

(1=very good, 

5=very poor)

Orientation 

confidence 

(1=very good, 

5=very poor)

Estimated 

length of 

reflector 

(meters)

Comments

206.6 0 85 5 5 121.6 lower limb

219.7 10 86 5 5 80.1 lower limb

228.0 220 78 2 4 39.4 lower limb

282.7 200 70 3 4 32.6 crossing

310.4 160 73 4 4 32.7 crossing

318.6 n/a 74 5 5 17.5 lower limb

329.1 100 82 2 2 72.1 lower limb

340.1 100 83 3 4 60.8 lower limb

364.2 120 80 3 2 40.1 lower limb

424.9 310 84 3 2 80.2 upper limb

426.1 350 77 4 4 63.5 crossing

451.4 140 73 4 5 29.1 upper limb

468.2 210 69 5 4 21.3 upper limb

540.2 110 87 4 5 133.6 upper limb

Depth from 

land surface 

(meters)

Strike 

(degrees)

Dip 

(degrees)

Reflector 

continuity 

(1=very good, 

5=very poor)

Orientation 

confidence 

(1=very good, 

5=very poor)

Estimated 

length of 

reflector 

(meters)

Comments

381.7 350 56 5 5 28.3 lower limb

406.8 170 63 5 5 14.2 lower limb

419.9 190 71 2 4 18.3 lower limb

426.6 190 58 3 4 19.4 crossing

434.6 180 63 4 4 23.6 crossing

Table 6. Planar reflectors interpreted from 60-megahertz radar reflection log, borehole HC-8, Project Shoal Area, 

Churchill County, Nevada

16 Analysis of Borehole-Radar Reflection Logs from Selected HC Boreholes at the Project Shoal Area, Churchill County, Nevada 
620

640

660

680

700

720

740

0 10000 20000 30000 40000

PEAK-TO-PEAK AMPLITUDE, IN 

MICROVOLTS

DEPTH BELOW TOP OF CASING, IN METERS

620

640

660

680

700

720

740

0.09 0.10 0.11 0.12 0.13 0.14 0.15

RADAR PROPAGATION VELOCITY, IN 

METERS PER NANOSECOND

DEPTH BELOW TOP OF CASING, IN METERS

0.0 0.1 0.2

TWO-WAY TRAVEL TIME, IN MICROSECONDS

0 5 10 15

RADIAL DISTANCE, IN METERS

650

700

DEPTH, IN METERS BELOW TOP OF C

ASING

AMPLITUDE,

IN

MICROVOLTS

10000

5000

2500

1000

-10000

-5000

-2500

-1000

-500

-250

-100

0

100

250

500

N

poor to very poor

good to very good

fair

(C) (D)

(A) (B)

Figure 10. Radar reflection logging in borehole HC-8, Project Shoal Area, Churchill County, Nevada: (A) 60-

megahertz magnetic-dipole directional radar reflection log, (B) lower hemisphere equal-area stereo-net showing 

poles of interpreted reflectors, (C) direct-wave amplitude log, (D) direct-wave radar velocity log.

RESULTS OF BOREHOLE-RADAR REFLECTION LOGGING AT THE PROJECT SHOAL AREA 17
SUMMARY AND CONCLUSIONS

Borehole-radar reflection logging using 

60-MHz omni-directional and directional antennas 

was conducted at the Project Shoal Area, Churchill 

County, Nevada. The overall quality of the radar data 

is marginal, ranging from very poor to good. Six 

boreholes were logged (HC-1, HC-2, HC-5, HC-6, 

HC-7, and HC-8), but the data from one borehole 

(HC-1) were uninterpretable. Of the five boreholes 

interpreted, four (HC-5, HC-6, HC-7, and HC-8) were 

logged using a directional receiving antenna capable 

of providing the information to determine the reflector 

orientation. 

Twenty-seven reflectors were interpreted 

from the directional radar reflection logs. Histograms 

summarizing the range of interpreted azimuths (strike) 

and dips are shown in figures 11 and 12. Azimuths are 

concentrated in two orientations — northeastsouthwest and east-west to slightly northwest -

southeast. Reflectors are moderate to steeply dipping. 

The mean reflector dip is 72.6°; the median is 73°

with a standard deviation of 10.1°. Reflector length 

was estimated for each reflector using a straight-ray 

reflection path approximation. Reflector length ranged 

from less than 7 to more than 133 m, with a mean of 

47 m, median of 34.5 m, and standard deviation of 

37.3 m.

Reflector quality scores from 1 (best) to 5 

(worst) were assigned to each reflector to provide a 

sense of the spatial continuity of the reflectors and the 

comparison of the field data relative to an ideal planar 

reflector. The average reflector continuity score is 3.6 

(fair to poor range, fig. 13), consistent with fractures 

or fracture zones that contain localized to moderate 

discontinuities but which are still relatively 

continuous over a scale of tens of meters. 

The orientation confidence scores are low, 

generally about 4.0 (fig. 14). The low scores reflect 

the general data quality, but also indicate that the 

behavior of most reflectors departs from the ideal 

planar case. The low scores are consistent with 

reflections from fracture zones containing numerous, 

closely spaced, sub-parallel fractures. 

An equal-area stereo-net that summarizes 

interpretations from all of the boreholes logged at the 

PSA is shown in figure 15. In general, the most 

continuous reflectors are those having the steepest 

dips, and either north-south or east-west strikes.

Direct-wave analysis performed on the radar 

reflection logs was used to generate logs of radar 

velocity and amplitude. Zones of low radar velocity 

correlate with decreases in direct-wave amplitude, 

most likely indicating the presence of saturated 

fracture zones. In boreholes HC-5, HC-6, and HC-7, 

direct-wave amplitudes increase with depth; this 

suggests an overall increase in electrical resistivity, 

possibly due to changes in mineral assemblage and

(or) to a decrease in the specific conductance of 

ground water. In boreholes HC-6 and HC-7, at depths 

below 300 m, the direct-wave amplitudes increase 

over the same interval where direct-wave velocities 

are decreasing. This observation is consistent with an 

increase in primary or secondary porosity coupled 

with a decrease in specific conductance of ground 

water, and (or) a change in mineral assemblage. 

Another observation is the similarity between the 

direct-wave logs from HC-6 and HC-7 when the HC-7 

log is shifted upward about 50 m. The similarities 

suggest that HC-6 and HC-7 are connected by 

structural features with a down-dip component in the 

direction of HC-7. The results of the borehole-radar 

reflection logging indicate that even where data 

quality is marginal, these data can provide useful 

information for ground-water characterization studies 

in fractured rock, and provide insights into the nature 

and extent of fractures and fracture zones in and near 

boreholes. 

18 Analysis of Borehole-Radar Reflection Logs from Selected HC Boreholes at the Project Shoal Area, Churchill County, Nevada
0

1

2

3

4

5

6

7

0 to

30

30 to

60

60 to

90

90 to

120

120 to

150

150 to

180

180 to

210

210 to

240

240 to

270

270 to

300

300 to

330

330 to

360

AZIMUTH, IN DEGREES

NUMBER OF REFLECTORS

0

2

4

6

8

10

12

0 to 10 10 to 20 20 to 30 30 to 40 40 to 50 50 to 60 60 to 70 70 to 80 80 to 90

DIP, IN DEGREES

NUMBER OF REFLECTORS

Figure 12. Distribution of interpreted borehole-radar reflectors sorted by dip, Project Shoal Area, Churchill 

County, Nevada.

Figure 11. Distribution of interpreted borehole-radar reflectors sorted by azimuth, Project Shoal Area, Churchill 

County, Nevada.

SUMMARY AND CONCLUSIONS 19
0

1

2

3

4

5

6

7

8

9

10

5 (very poor) 4 (poor) 3 (fair) 2 (good) 1 (very good) 

CONTINUITY OF REFLECTORS

NUMBER OF REFLECTORS

Figure 13. Distribution of interpreted borehole-radar reflectors sorted by the continuity of the reflectors, Project 

Shoal Area, Churchill County, Nevada.

0

2

4

6

8

10

12

14

5 (very poor) 4 (poor) 3 (fair) 2 (good) 1 (very good)

ORIENTATION CONFIDENCE

NUMBER OF REFLECTORS

Figure 14. Distribution of interpreted borehole-radar reflectors sorted by orientation confidence, Project Shoal 

Area, Churchill County, Nevada.

20 Analysis of Borehole-Radar Reflection Logs from Selected HC Boreholes at the Project Shoal Area, Churchill County, Nevada
Figure 15. Lower hemisphere equal-area stereo-net showing poles of all interpreted radar reflectors, weighted 

by reflector length and combined reflector quality, Project Shoal Area, Churchill County, Nevada.

good to very good

fair

poor to very poor

SUMMARY AND CONCLUSIONS 21
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Microprocessor-based data-acquisition system for 

a borehole radar: IEEE Transactions on 

Geosciences and Remote Sensing, GE-24, p. 441-

447.

Cohen, P., and Everett, D., 1963, A brief appraisal of 

the ground-water hydrology of the Dixie-Fairview 

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Department of Conservation and Natural 

Resources, Ground-Water Resources 

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Cook, J.C., 1975, Radar transparencies of mine and 

tunnel rocks: Geophysics, v. 40, no. 5, p. 865-885.

Falk, L., 1992, Directional borehole antenna--theory, 

Stripa Project 92-16, SKB: Stockholm, Sweden, 

138 p.

Gaylor, R., Lieblich, D.A., Mariani, D., and Xia, J., 

1994, Environmental logging with a borehole radar 

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Electromagnetics, April 5-7: New York, New York 

Polytechnic University, 20 p.

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Haeni, F.P., Lane, J.W., Jr., and Lieblich, D.A., 1993, 

Use of surface-geophysical and borehole-radar 

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Hampshire in Banks, S., and Banks, D., (eds.) 

Hydrogeology of Hard Rocks: Memoires of the 

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Geological Survey of Finland Special Paper 16, p. 

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Lane, J.W., Jr., Haeni, F.P., and Williams, J.H., 1994, 

Detection of bedrock fractures and lithologic 

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Nilsson, B., 1983, A new borehole radar system, in

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geophysics--mining and geotechnical applications: 

Toronto, Canada, 400 p.

Olsson, O., Andersson, P., Carlsten, S., Falk, L., Niva, 

B., and Sandberg, E., 1988, Fracture 

characterization in crystalline rock by borehole 

radar: Workshop on Ground-Penetrating Radar, 

May 24-26, Ottawa, Canada, 24 p.

Olsson, O., Anderson, P., Carlsten, S., Falk, L., Niva, 

B., and Sandberg, E., 1992a, Fracture 

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150.

Olsson, O., Falk, L., Forslund, O., Lundmark, L., and 

Sandberg, E., 1992b, Borehole radar applied to the 

characterization of hydraulically conductive 

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Pohll, G., Chapman, J., Hassan, A., Papelis, C., 

Andricevic, R., and Shirley, C., 1998, Evaluation 

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Rubin, L.A., Fowler, J.C., and Marino, G.G., 1978, 

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Sandberg, E.V., Olsson, O. L., and Falk, L. R., 1991, 

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tomography, and directional borehole-radar data: 

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Stevens, K.M., Lodha, G.S., Holloway, G.S., and 

Soonawala, N.M., 1995, The application of ground 

penetrating radar for mapping fractures in plutonic 

rocks within the Whiteshell Research area, Pinewa, 

Manitoba, Canada: Applied Geophysics, v. 33, no. 

1-3, p. 125-143.

22 Analysis of Borehole-Radar Reflection Logs from Selected HC Boreholes at the Project Shoal Area, Churchill County, Nevada
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chemical, and hydrological investigations of the 

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REFERENCES CITED 23