Remote sensing was included in a comprehensive investigation of the use of geophysical techniques to aid in underground mine placement. The primary objective was to detect faults and slumping, features which, due to structural weakness and excess water, cause construction difficulties and safety hazards in mine construction. Preliminary geologic reconnaissance was performed on a potential site for an underground oil shale mine in the Piceance Creek Basin of Colorado. LANDSAT data, black and white aerial photography and 3 cm radar imagery were obtained. LANDSAT data were primarily used in optical imagery and digital tape forms, both of which were analyzed and enhanced by computer techniques. The aerial photography and radar data offered supplemental information. Surface linears in the test area were located and mapped principally from LANDSAT data. A specific, relatively wide, linear pointed directly toward the test site, but did not extend into it. Density slicing, ratioing, and edge enhancement of the LANDSAT data all indicated the existence of this linear. Radar imagery marginally confirmed the linear, while aerial photography did not confirm it

Jackson, P. L.

Ruskey, F.

Shuchman, R. A.

Wagner, H.

English

NASA Technical Reports Server

N78-14561
INTEGRATION OF REMOTE SENSING AND
SURFACE GEOPHYSICS IN THE DETECTION OF FAULTS
P.L. Jackson
R.A. Shuchman
H. Wagner
Environmental Research Institute of Michigan
Ann Arbor, Michigan
F. Ruskey
Denver Mining Research Center
U.S. Bureau of Mines
Denver, Colorado
ABSTRACT
Possible faults indicated by remote sensing can be
quickly confirmed by resistivity surveys. Anomalous
resistivity values occur within the fault crush zone.
In a sedimentary region in Rio Blanca County, north-
west Colorado, a fault zone was inferred from LANDSAT
imagery. Subsequent resistivity surveys indicated
substantial resistivity highs associated with the
faults. Seismic data and the drilling of an
observation well confirmed the main fault.
1. INTRODUCTION
Remote sensing was included in a comprehensive investigation of the use of
geophysical techniques to aid in underground mine placement. The primary
objective was to detect faults and slumping, features which, due to structural
weakness and excess water, cause construction difficulties and safety hazards
in mine construction.
Preliminary geologic reconnaissance was performed on a potential site for
an underground oil shale mine in the Piceance Creek Basin of Colorado. LANDSAT
data, black and white aerial photography and 3-cm radar imagery were obtained.
LANDSAT data were primarily used in optical imagery and digital tape forms, both
of which were analyzed and enhanced by computer techniques. The aerial photo-
graphy and radar data offered supplemental information.
Surface linears in the test area were located and mapped principally from
LANDSAT data. A specific, relatively wide, linear pointed directly toward the
test site, but did not extend into it. Density slicing, ratioing, and edge
enhancement of the LANDSAT data all indicated the existence of this linear.
Radar imagery marginally confirmed the linear, while aerial photography did not
confirm it.
A resistivity mapping survey through the test site and perpendicular to the
remotely sensed linear indicated a substantial resistivity anomaly (high) across
an extension of the linear. A parallel resistivity survey line confirmed that
the anomaly was aligned with the linear. Resistivity differences between fault
zones and their environs are due to the comparatively high moisture content with-
in the zone to produce a resistivity low, and, either calcification or drainage
of moisture (leaving comparatively large interstices) to produce a resistivity
high.
1137
https://ntrs.nasa.gov/search.jsp?R=19780006618 2020-03-22T05:46:02+00:00Z
The existence of the faults were further confirmed by a refraction seismic
survey, and by drilling an observation well in which rubble was found, indicating
a fault crush zone.
2. GEOLOGIC SETTING OF TEST SITE
The area of concentration for this study is Igcated in Fault Draw, a sub-
tributary valley of Ryan Gulch at approximately 39 55' north latitude and 108
20' west longitude (section 6, R 97W, T 2S). Ryan Gulch is situated in the
north-central part of the Piceance Creek Basin, Rio Blanco County, Colorado.
Fault Draw is important, for here the U. S. Bureau of Mines initiated a test
drilling to determine the feasibility of an underground oil shale mining
operation. Figure 1 is a topographic map of the test site area.
Structurally, the test site lies about 15 kilometers from the center of a
domal uplift where commercial gas fields are found. The arcuate shape of
Piceance Creek indicates that it is a consequent stream to this domal uplift. A
graben and its associated topographical expression (Dudley Bluffs) extends at
least 25 km from Collins Gulch in the domal uplift to Yellow Creek, which is
about 9 km west-northwest of the test site. As this extensive structural
feature passes closely by or encompasses the test site, which is also close to
the large domal uplift, other structural features such as tension faulting would
be plausible in this region.
Bedrock exposed at the Fault Draw/Ryan Gulch area is yellow-brown sandstone
of the Uinta Formation. It can be seen along the valley walls and especially at
the junction of the two valleys. Near the mouth of Fault Draw along the north-
western wall of Ryan Gulch are the best exposures, where visible evidence of the
Dudley graben can be found. Running across Ryan Gulch and bordering near the
mouth of Fault Draw are two normal faults which form the graben. Within the
sandstone outcrop northeast of the mouth of Fault Draw can be seen a white
segment of calcite, presumably filling the southern member of the pair of faults.
The vertical displacement of the graben is approximately 50 feet.
Extensive jointing, characteristic of the Uinta Formation throughout the
basin, results in poor resistance to weathering, and makes the formation one of
the principal aquifers of the area. Random outcrops of bedrock core appear
through the unconsolidated materials which blanket and shape the rolling hills.
3. REMOTE SENSING DATA
Three types of remote sensing data were used in the study: black and white
aerial photography, X-band synthetic aperture radar (SAR) imagery, and four-
channel MSS LANDSAT data. These three types of imagery are available to the
public at nominal cost and with little delay. Particularly with the more
sophisticated LANDSAT and SAR data, an array of interpretive techniques can be
used. These techniques range from simply viewing and interpreting a single
image to that of complexly performing computer analysis using statistical and
other comparisons of several images. In this study several computer analysis
techniques were used on the imagery.
The LANDSAT data was the primary source of finding unmapped linears.
Aerial photography and imaging radar data provided supplemental information.
The four channels of LANDSAT data are shown in Figure 2.
An alternative format of LANDSAT data is computer compatible tape, which
can be exploited on the computer. Computer analysis involved level slicing
single and two-channel ratio images to attempt to determine whether any
structural or lithological information could be obtained about fault systems in
the area. The image, a "graymap", is composed of selected symbols on a computer
printout. The computer analysis was performed on the University of Michigan
1138
AMDAHL computer using a Department of Natural Resources LIGMALs program. The
black and white stereo aerial photography with a scale of 1:60,000 is shown in
Figure 3. Piceance Creek and Ryan Gulch form the partially cut off "A" in the
lower right-hand corner of the image. The cross of the "A" is a portion of a
long linear composed of Dudley Bluffs and associated graben which is oriented
approximately N25E. Aerial photography provided supplemental data in the form
of topographic, vegetation and stream pattern information.
Side looking radar imagery was also utilized in the study. The synthetic
aperture radar (SAR) imagery was obtained with a wavelength of 3 cm (X-band)
radar (Brown and Porcello, 1969). The imagery was provided courtesy of the
Strategic Air Command, and is available from Goodyear Aerospace Corporation,
Litchfield, Arizona.
4. INTERPRETATION OF REMOTE SENSING
Several linear features are interpreted as faults which geologic maps of
the area confirm. There are some structures noted on the imagery as suspected
faults which have not been mapped on the geologic maps. Trexler (1974) mapped
anticlincal and synclincal folds and faults throughout the Piceance Basin using
photographic interpretive techniques on single channel LANDSAT images.
Stereo photographs (Fig. 3) confirm some but not all of the geologic
structures discerned on LANDSAT. Near the test site, Dudley Bluffs with its
associated fault zone are clearly visible on both LANDSAT and aerial photography.
However, the aerial photography only indicates a single fault feature - Dudley
graben. A more dense band of vegetation at the known location of the graben
appears to be a result of the zone of brecciation and consequent moisture within
the graben.
Figure 4 is a 5/7 ratio processed graymap produced by point-by-point
ratioing of LANDSAT Band 5 by Band 7. The "A" (without the cross) in the upper
portion of the figure is the intersection of Ryan Gulch and Piceance Creek.
The ratioing process performed in this image tends to suppress variation in
illumination due to topography and viewing angle. For example, Dudley Bluffs
and graben (the cross of the "A") is suppressed in this figure. Thus, differences
in this image can be attributed to variations in the composition (i.e.,
lithography, mineralogy, moisture, vegetation) rather than the topography. The
5/7 image clearly delineates the alluvial deposits (chiefly silt, sand, and
gravel) from the surrounding green river bedrock (gray and yellow-brown marl-
stone, siltstone, sandstone and tuff).
In the middle of the upper portion of Figure 4, above the Ryan Gulch -
Piceance Creek intersection, a bright linear about 1/8 inch in width can be
seen. The extension of this linear extends directly through the test site.
This is the linear which aligned with the resistivity anomaly, and an observation
well at Fault Draw which indicated faulting. This extension into Fault Draw is
termed Burdick's Fault. Aligned with this linear, but not extending as far
south as shown on LANDSAT imagery, are a series of three faults shown by
Welder (1971).
It is this linear which demonstrates the utility of commencing reconnais-
sance with the easily available, inexpensive remote sensing data. This linear
is not associated with topography, and therefore had been previously overlooked
as a possible fault zone.
Figure 5 is a channel 5 density sliced image that is intended to show a
series of linears in close proximity to the test site. Linear A appears to be
the same linear enhanced on the 5/7 ratio image previously shown.
The final sets of results are edge enhanced images of LANDSAT band 5 and
the 3 cm SAR data. The image enhancer is a spatial data color enhancer loaned
1139
to ERIM by Spatial Data Corporation of Goleta, California. An edge enhancement
mode that accents subtle density differences was used for this study. Through
edge enhancement a series of linears were displayed that run northeast-southwest
through Piceance Dome into the test site. These linears were not indicated on .
geologic maps of the area. Linears in other directions were also displayed.
Figure 6 shows the normal Band 5 LANDSAT image, along with the resulting
edge enhanced image of the test site. The linear aligned with the resistivity
anomaly through the test site is evident on both images.
In Figure 6, note the clear indication of a linear aligned with Ryan Gulch
extending northeast toward the White River uplift. Although outside our test
area, this long, persistent linear concerns the test area. If this linear were
subsequently proven to be a fault through further geologic or geophysical
investigation, it would indicate more structural activity than previously
thought to be the case within the test region. Also, the straight portion of
Ryan Gulch might be fault controlled. This northeast linear is also present on
the four LANDSAT channels shown in Figure 2. Figure 7 is a SAR image of the
test site area which does not indicate this linear.
5. GEOPHYSICAL CONFIRMATION
Because a fault crush zone consists of broken particulate matter, it usually
possesses a different resistivity than the surrounding country rock. Resistivity
highs are produced by crystallization or calcification due to fluid transport
within the fault, or by relatively large particles which do not retain water.
Resistivity lows are produced by the retention of water by relatively small
particles within the fault zone.
Mapping resistivity surveys across a suspected fault can be used to confirm
the existence of a fault. An economical and timely method of resistivity mapping
is that of taking successive measurements along a baseline using a Wenner array
(Parasnis, 1966). This simple configuration consists of four in-line electrodes
equally spaced. The two current electrodes are at the ends of the line, the
two voltage electrodes near the center. Under conditions of constant current
input through the current electrodes, the voltage difference between the
voltage electrodes indicates the apparent resistance of the earth under the
electrodes. The effective depth of measurement is proportional to the spacing
of the electrodes. If the array of electrodes is moved with successive
measurements along a line crossing a resistivity anomaly, a plot will indicate
the location of the anomaly.
At our test site resistivity was mapped across the area which the extension
of the remotely sensed linear indicated. Fifty foot electrode spacing was used.
A substantial resistivity high was found. Resistivity was then mapped 400 meters
away on a line parallel to the first line, and another substantial resistivity
high was again found. The two resistivity highs aligned with the remote sensed
linear.
Figure 8 is a photograph of the test site showing the placement of the
resistivity survey lines. The dashed line represents the location of the
inferred fault. Figure 9 shows the resistivity profiles of the two lines. The
first had an anomalous, apparent resistivity high of 750 ohm meters, the second
of 1600 ohm meters. The average resistivity in this region is approximately
100 ohm meters. In Figure 9 the two lines showing the substantial resistivity
high were on elevations away from the alluvium of the draw. Two more lines,
between the outer two, are on alluvium, and show modes rises when crossing the
fault.
The fault was fully confirmed by drilling, and later by a seismic survey
with 20-foot spaced geophone arrays.
1140
6. DISCUSSION
One of the major geological uses of remote sensing has been the mapping
of previously unknown linears. Both LANDSAT and synthetic aperture radar
imagery have proven very useful in such mapping. In many cases these linears
turn out to be faults.
These faults can be confirmed by surface geophysical measurements, one of
the most economical and timely being resistivity. Several advantages of
resistivity surveys are:
1. Instrumentation is simple and comparatively inexpensive.
2. Minimal skill is required of a small crew.
3. Data can be gathered under any noise condition, such as
heavy machinery.
4. Immediate reduction of the data enables one to search out
the geometry of the anomaly during the data gathering
phase.
5. The data, although not uniquely interpretable, are in a
straightforward form that is easily and clearly under-
stood by the non-geophysicist.
Although the experiment conducted here was for mine placement, the
confirmation of faults by resistivity can aid in solving other problems. For
example, in searching for underground water sources in arid and semi-arid
regions. In these regions sources of water are often fault controlled. A
relatively inexpensive resistivity mapping survey would greatly improve the
confidence that water might be found before commencement of expensive drilling.
Depending upon the cost of the operation to be performed--whether mine
placement, water drilling, mineral exploration, etc.--other surface measurement
techniques such as seismics can be used for further confirmation of the
existence of faults.
1141
uH
 
i
 
*w
I-I
 
•!-{
 
O
 C
CO
 
J-lO
 
C
H
 £
 O
re
H
 re
 re
 e
n
s
vi
 
u
 co
 re
fr
,
 
4
_
)
 O
 
V
j
O
 
C
 
-
-I
 C
O
 O
Q
>
 
O
 i—
'
O
<
 
O
 
<U
 CO
 
O
<5
 
.c
 3
 o
"
"
 o
O
 
M
 
01
M
 
<U
 
-i-l
 
•
 i—
I
JC
 
H
 
i-l
 
0
0
0-i
 
tfl
 
Q)
 i—
I
 C
<
 3
 C
 <
u
 re
O
 
w
 i-i
 
"O
o
 
c
 re
cu
 ^
 
c
 o
 3
o
 
o
 o
 
-i-i
 o
*
H
 re
 i-i
 4J
^-i
 u
 re
 £
.
pa
 o
 
>
 o
a)
 
^
 C
i—i
 
w
 
cu
 re
CO
 
OS
O
 O
 
C
 
<
U
M
 W
 O
 X
b
.
 
B
d
 N
 4-1
1142
ORIGINA
L
 PA
G
E
 IS
O
F
 POOR
 QUALITY
I
01
X
 C
<C
 
H
 
r-t
 
<
U
oi
 z
 
>
-
"
 <
u
 
o
o
 M
 PQ
 >
O
 
-H
 c
.
Q
 PL
,
 in
 
4-1
 
O
W
 
I
 
to
 4-1
C/3
 
>H
 Q
 
i-l
cn
 CQ
 z
 
a)
 
-i-J
W
 
i
 
<
 
iJ
 
CO
u
 H
 o
a
O
 Z
 
-
 M
a
,
 in
 M
 c
O
 
Q
 
-H
 
-H
M
 
>
-<
 
Z
 
i—
(
 i—
<
H
 CQ
 <
<;
 
J
 
oj
 I-H
PS
 a
 
u
 <o
W
 b
 
O
 O
O
 O
 Z
 T
-l
•
*
 O
 O
 
M
O
 Z
 
•
 fl)
a;
 a
.
 o
o
 
M
 Q
 v
O
 P
-i
 H
 Z
 T
3
uHt/3HwHoHoPL!wHWa:u
1143
H
O
fc
,
 M
W
 Q
i
u
W
H
O
 Men
in
 wH
a2
 P
L
,
<
0
PQ
M
H
O
O
 (-1
<
Q
J
 Woz
w
 u
33
 W
O
O
M
Q
U
 
co
 at
O
 (0
 ai
W
 JS
 ffl
u
 o
o
o
M
 
-H
 
-H>
-
ai
M
 
0)
W
 Q
 T
3
Z
 Z
 i-l
W
<
 3
Q
 03
00
H
 C
•
<
 O
in
 co
 i-i
Q
 
«
u
 z
B:«£
 vj
oJ
 D
o
 
o
M
 
P
L
,
 O
PL
,
 O
 
O
1144
HM
 
I
W
 >
 W
 2
H
 
w
 Z
 M
i—
i
 H
 M
co
 co
 ,J
 ac
M
 
O
H
 C
O
 Q
 l-l
w
 os
 ac
 §
 
•
H
 
c
o
 
H
-<
 
C
O
 
,
-J
ft
,
 i-l
 Q
 BC
 D
O
 iJ
 
O
 <
W
 O
 M
 b
<
3C
 S
 z
 a
c
O-
,
 
<
 
W
2
 O
 
-E->
 H
O
 M
 c
o
 M
O
 H
 W
 >
 c
o
O
 >
 M
 H
 H
ac
 os
 
.
-I
 co
 <
P
-i
 W
 
M
O
CO
 O
 
C
O
 M
CQ
 M
 W
 Q
•
 o
 a
 os
CO
 
CO
O
 M
 ffi
W
 2
 W
 O
OS
 M
 co
 D
3
3
 
O
O
 O
 Q
 ft
ft
,
 CO
 <
 H
oHoWoiWHHCOWHOS<COWOS
1145
ORIGINAL
 PAGE
 IS
OF
 POOR
 QUALITY
c
o
c
o
3
 
.
£.!?
•
§
 
~
§i- §§°CM UW
.
 (U0)
H
 W
W
 H
M
 1-1
W
 COCO
H
 W
2
 H, in
:
 az
Ed
 O
UM
 3
&L
.
 O
U
.IA
IISISX
I
1146


Integration of remote sensing and surface geophysics in the detection of faults

Abstract

Similar works

Full text

Available Versions

NASA Technical Reports Server