Geophysical Studies of the Crump Geyser Known

Geothermal Resource Area, Oregon, in 1975

By Donald Plouff

2006

Open-File Report 2006–1110

U.S. Department of the Interior

U.S. Geological Survey 
ii

U.S. Department of the Interior

Gale A. Norton, Secretary

U.S. Geological Survey

P. Patrick Leahy, Acting Director

U.S. Geological Survey, Reston, Virginia 2006

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iii

Contents

Discussion ................................................................................................................................................ 1

Acknowledgments..................................................................................................................................... 2

References Cited ...................................................................................................................................... 3

Appendix 1—Administrative report, June 17,1975 ....................................................................... attached

Appendix 2—Reprint of NTIS publication PB-245-426/AS........................................................... attached
1

Geophysical Studies of the Crump Geyser Known

Geothermal Resource Area, Oregon, in 1975

By Donald Plouff

Discussion

The U. S. Geological Survey (USGS) conducted geophysical studies in support of the resource appraisal

of the Crump Geyser Known Geothermal Resource Area (KGRA). This area was designated as a

KGRA by the USGS, and this designation became effective on December 24, 1970 (Godwin, and 

others, 1971). The land classification standards for a KGRA were established by the Geothermal Steam

Act of 1970 (Public Law 91-581). Federal lands so classified required competitive leasing for the

development of geothermal resources.

Donald Plouff presented an administrative report of USGS geophysical studies entitled “Geophysical

background of the Crump Geyser area, Oregon, KGRA” to a USGS resource committee on June 17,

1975. This report, which essentially was a description of geophysical data and a preliminary 

interpretation without discussion of resource appraisal, is in Appendix 1. Reduction of sheets or plates

in the original administrative report to page-size figures, which are listed and appended to the back of

the text in Appendix 1, did not seem to significantly degrade legibility. Bold print in the text indicates

where minor changes were made. A colored page-size index and tectonic map, which also show

regional geology not shown in figure 2, was substituted for original figure 1. Detailed descriptions for

the geologic units referenced in the text and shown on figures 1 and 2 were separately defined by 

Walker and Repenning (1965) and presumably were discussed in other reports to the committee. Heavy 

dashed lines on figures 1 and 2 indicate the approximate KGRA boundary

Units of measurement such as miles and feet and corresponding map scales were in the original report,

but international units such as meters and kilometers now are preferred. The distance unit “meter”

originally was spelled “metre” in Appendix 1 in accordance with the conventional international and

USGS usage in 1975. For conversion to Standard International Units:

1 foot = 0.3048 meter

1 mile = 1.609 kilometer

1 g/cm3 = 1,000 kg/m3

1 gamma = 1 nanotesla

One of the principal results of the geophysical studies was to obtain a gravity map (Appendix 1, fig. 10;

Plouff, and Conradi, 1975, pl. 9), which reflects the fault-bounded steepness of the west edge of

sediments and locates the maximum thickness of valley sediments at about 10 kilometers south of

Crump Geyser. Based on the indicated regional-gravity profile and density-contrast assumptions for the
2

two-dimensional profile, the maximum sediment thickness was estimated at 820 meters. A threedimensional gravity model would have yielded a greater thickness. Audiomagnotelluric measurements

were not made as far south as the location of the gravity low, as determined in the field, due to a lack of

communication at that time. A boat was borrowed to collect gravity measurements along the edge of

Crump Lake, but the attempt was curtailed by harsh, snowy weather on May 21, 1975, which shortly

followed days of hot temperature.

Most of the geophysical data and illustrations in Appendix 1 have been published (Gregory and 

Martinez, 1975; Plouff, 1975; and Plouff and Conradi, 1975), and Donald Plouff (1986) discussed a

gravity interpretation of Warner Valley at the Fall 1986 American Geophysical Union meeting in San

Francisco. Further interpretation of possible subsurface geologic sources of geophysical anomalies was

not discussed in Appendix 1. For example, how were apparent resistivity lows (Appendix 1, figs. 3-6)

centered near Crump Geyser affected by a well and other manmade electrically conductive or magnetic

objects? What is the geologic significance of the 15-milligal eastward decrease across Warner Valley?

The explanation that the two-dimensional gravity model (Appendix 1, fig. 14) was based on an inverse

iterative method suggested by Bott (1960) was not included. Inasmuch as there was no local subsurface

rock density distribution information to further constrain the gravity model, the three-dimensional

methodology suggested by Plouff (1976) was not attempted.

Inasmuch as the associated publication by Plouff (1975), which released the gravity data, is difficult to 

obtain and not in digital format, that report is reproduced in Appendix 2. Two figures of the publication

are appended to the back of the text. A later formula for the theoretical value of gravity for the given 

latitudes at sea level (International Association of Geodesy, 1971) should be used to re-compute gravity 

anomalies. To merge the observed-gravity values printed in that report with later measurements, an 

empirically determined constant gravity datum shift should be applied. USGS reports in the Open-File

series can be downloaded from the Publication Warehouse at:

http://pubs.er.usgs.gov/pubs/ofr/

Acknowledgments

Marshall J. Reed suggested that the previously unpublished administrative report, although informally

prepared, should be released to the public as a historical record and for possible present day application.

He also described how KGRA’s fit into the resource appraisal system and greatly simplified my effort

by obtaining and scanning original texts, plates, figures, and tables. Frank A. Petrafeso, chief of the

aeromagnetic compilation unit in 1975, supplied the unpublished aeromagnetic map. Donald B. Hoover

supplied figures and wrote the rough draft of the audiomagnetotelluric text to be incorporated in the

administrative report. Carl Long provided further understanding of audiomagnetotelluric methodology.

Arhur Conradi, Jr. assisted in the field and office for gravity and ground magnetic studies. Nicholas

Voegtly, Water Resources Division, assisted in the field.
3

References Cited

Bott, M.H.P., 1960, The use of rapid digital computing methods for gravity interpretation of

sedimentary basins: Geophysical Journal of the Royal Astronomical Society, v. 3, p. 63-67.

Godwin, L.H., Haigler, L.B., Rioux, R.L., White, D.E., Muffler, L.J.P., and Wayland, R.G., 1971,

Classification of public land valuable for geothermal steam and associated geothermal resources: U.S.

Geological Survey Circular 647, 18 p.

Gregory, D.I., and Martinez, R.J., 1975, Audio-magnetotelluric apparent resistivity maps, southern 

Warner Valley, Lake County, Oregon: U.S. Geological Survey Open-File Report 75-652, 4 sheets.

International Association of Geodesy, 1971, Geodetic reference system 1967: International Association 

of Geodesy Special Publication no. 3, 116 p.

Plouff, Donald, 1975, Gravity data in Crump Geyser area, Oregon: National Technical Information

Service, PB-245-426, 16 p.

Plouff, Donald, 1976, Gravity and magnetic fields of polygonal prisms and application to magnetic

terrain corrections: Geophysics, v. 41, no. 4, p. 727-741

Plouff, Donald, and Conradi, Arthur, Jr.,1975, Gravity and magnetic profiles and maps, Crump Geyser

area, Oregon: U.S. Geological Survey Open-File Report 75-346, 2 p., 12 sheets.

Plouff, Donald, 1986, Role of magma in localization of basin-range valleys [abs.]: American 

Geophysical Union Transactions (Eos), v. 67, no. 44, p. 1226.

Walker, G.W., and Repenning, 1965, Reconnaissance geologic map of the Adel quadrangle, Lake,

Harney, and Malheur Counties, Oregon: U.S. Geological Survey Miscellaneous Geologic

Investigations Map I-446, 1 sheet.
APPENDIX 1—ADMINISTRATIVE REPORT, JUNE 17,1975

[Bold print indicates minor modification of original report;

list of figures is on last page of text.]

Geophysical background of the

Crump Geyser, Oregon, K. G. R. A.

By

Donald Plouff

U.S. Geological Survey

Menlo Park, California

This report is preliminary and has

not been edited or reviewed for

conformity with Geological Survey

standards and nomenclature.
1

LOCATION

The Crump Geyser Known Geothermal Resource Area (Crump Geyser KGRA) is located

in Lake County, Oregon. The area of interest extends southward from the north edge

of Crump Lake to the south edge of Warner Valley and continues southward to the

Nevada border (Figure 1). The town of Adel is located near the center of the area.

The occurrence of Crump Geyser at the west central edge of the valley and a hot

spring at the northeast edge of the valley indicate potential development as a

geothermal resource area.

GEOLOGIC BACKGROUND

The geologic map of G. W. Walker and C. A. Repenning (1965, Reconnaissance

geologic map of the Adel quadrangle, Lake, Harney, and Malheur Counties, Oregon:

U.S. Geol. Survey Misc. Geol. Inv. Map I-446) provides the basis for interpretation

of the geophysical data collected near the Crump Geyser KGRA. Figure 1 is

reproduced from the map of Walker and Repenning, and Figure 2 is enlarged to

closely match the 1:62,500 map scale used in the following report. Problems of

photographic reproduction, however, resulted in a slightly mismatching scale of

about 1:61,200.

Warner Valley lies within the Basin and Range province and is a typical faulted

basin, elongated in the north-south direction. The mapped surface faults--with

upthrown sides to the west--near the west edge of Warner Valley form a fairly

continuous north-south belt (Tectonic Sketch Map, Figure 1). The east edge of

Warner Valley is bordered by faults with upthrown sides to the east only near the

hot springs and a northwest trending fault along the northeast edge of Greaser

Reservoir. A fairly continuous, though highly complicated, belt of north trending

faults with upthrown sides to the east, however, appears to project southeast and

thence southward from the vicinity of the hot springs to join with a fault at the

east edge of Coleman Valley.

The mountains surrounding Warner Valley are primarily composed of a thick,

complexly-faulted sequence of Tertiary rocks. Three Tertiary rock units are

indicated by Walker and Repenning within the area of geophysical surveys. The

oldest unit, labeled Tbf, consists of massive basalt flows and minor beds of tuff

and scoria. The unit of intermediate age, Tts, mostly consists of fine-grained

tuffaceous sedimentary rocks and tuffs. The youngest Tertiary unit, Tb, consists

of basalt flows, which generally dip 5 to 10 degrees.

GEOPHYSICAL METHODS USED

The audio-magnetotelluric method (AMT) is used to map electrically conductive

bodies. The method is used in geothermal areas to search for conductivity

anomalies associated with hot saline waters and related altered rock. About 20

man-days were spent collecting audio-magnetotelluric data near Warner Valley.

The magnetic method is used to detect changes in the magnetic properties of

rocks. The method can be used to detect the location of the continuation of faults

beneath alluvium, to detect contacts between rocks of different types, and to

determine the thickness of alluvium over magnetic basement rock. Six man-days were

spent in the field collecting magnetic data with a continuously-recording,

truckborne magnetometer. An aeromagnetic survey was flown to provide more complete

coverage of the area.
2

The gravity method is used to map geologic bodies on the basis of changes of

rock density. The method can be used to estimate the configuration of the bedrock

surface beneath alluvial valleys and to determine the location of concealed faults.

Twenty-seven man-days were spent in the field collecting gravity data.

AUDIO-MAGNETOTELLURIC SURVEY

The audio-magnetotelluric (AMT) method is an electromagnetic exploration

technique which uses energy derived from world-wide lightning storms to measure

variations in earth resistivity as a function of depth and position. The U.S.

Geological Survey is using AMT methods for reconnaissance surveys in geothermal

areas because it is a fairly fast, simple, and effective means of mapping

resistivity variations at moderate depths. The depth of exploration is a function

of both the frequency of the received signal and the resistivity of the lithologic

section. The maximum exploration depth is approximately one skin depth, D, which

for a homogeneous half-space is given by

D = 503 (R/f)1/2 meters,

where R is the resistivity in ohmmeters and f is the frequency in Hertz. This

equation can be used to roughly estimate the exploration depths at each AMT station

(Figures 3-6), using the frequency for the given map and the apparent resistivity

at that station.

The electric component of the electromagnetic field is the time-varying

difference of potential between a pair of steel electrodes separated at a distance

of 100 meters. The orthogonal, horizontal magnetic component is detected with a

sensor that consists of thousands of turns of wire wrapped around a ferrite core.

The voltage changes are measured by using matched, narrow-band, selectively-tuned

voltmeters. Apparent resistivities were calculated at frequencies centered at 7.5,

27, and 285 Hz along components in the north-south and east-west directions.

Each of the four apparent resistivity maps (Figures 3-6) indicates a general

resistivity low centered near Crump Geyser. Using the four-ohmmeter contour as an

arbitrary dividing line, the part of the resistivity low associated with the most

conductive underlying rocks encloses a surface area of less than two square

kilometers. The low is bounded on the south by a relative resistivity high, which

tends to cross Warner Valley at about 3 to 7 km south of Crump Geyser.

The shapes of the contour lines, especially to the west of Crump Geyser were

guided by numerical interpolation rather than by geologic inference. In view of

the occurrence of marked geologic changes along the escarpment to the west of Crump

Geyser, the association of the valley AMT low with a distant station to the west

(especially noticeable at 7.5 Hz) is unlikely. A closer station spacing, which is

infeasible to the west, more likely might result in D-shaped contours that are

convex to the east.

The small high south of the prominent low (Figure 5) may indicate a zone of

alluvium which has been indurated by an earlier cycle of thermal activity. A small

low resistivity nose near the east edge of the valley (Figures 4 and 5) might

indicate thermal water rising along a fault.

The apparent resistivity value at the sounding near Crump Geyser increases from

1.7 or 1.8 ohmmeters on the 27 Hz maps to 2.5 ohmmeters on the 7.5 Hz map (Figure

6). A decrease in frequency is equivalent to an increase in the depth or distance

of penetration of the electromagnetic wave. The deeper-penetrating, lower-
3

frequency sounding indicates a high resistivity layer at depth or indicates the

edge of a relatively narrow conductive zone. The latter interpretation seems

likely at this location because the thermal waters leaking to the surface probably

are controlled by faulting near the west edge of the valley. The lack of other

conductivity anomalies along the fault zone probably indicates that it is sealed to

rising thermal waters. The audio-magnetotelluric data indicate that thermal waters

in Warner Valley are probably fault-controlled in the upper part of the geologic

section, but no extensive shallow reservoir exists within the surveyed area.

MAGNETIC SURVEYS

Truckborne magnetometer

Twelve truckborne magnetometer traverses are located near the Crump Geyser area

(Figure 7). A fluxgate magnetometer, mounted about four meters above the ground

surface, was used to continuously measure the earth's total magnetic field. The

original paper chart records of the total field measurements were photographically

reduced to a scale of about 1:60,000, which is nearly the same distance scale as

other figures of this report. Circled numbers on the magnetic records (Figures 8a8f) refer to location-points on the traverse map (Figure 7).

The scale on the magnetic records is 200 gammas between numbered chart lines.

Datum shifts caused by rapid changes of the magnetic field often were needed to

maintain the pen position between chart lines numbered 0 to 12. The closest fourdigit push-button setting (pbs) number indicated to the right of a record section

is used to convert amplitudes on the chart, in terms of interpolated chart line

numbers, N, to values of the absolute total magnetic field, T (in gammas). The

conversion formula is

T = 48,200 + 200N + 2000P1 + 400P2 + 100P3 + 20P4,

where P1 to P4 are the respective digits in a left-to-right sequence for the push

button setting.

Man-made objects such as culverts, bridges, vehicles, and cattle-guards produce

sharp spikes on the magnetic record, which interfere with recognition of anomalies

that result from geologic changes. The instrument operator has crossed out all of

the anomalies that are caused by recognized man-made objects, but others may remain

undetected.

The magnetic profiles (Figures 8a-8f) have been annotated to indicate the

locations of possible faults or geologic contacts. The interpretation of these

locations is based on a change in character along the magnetic record. The change

in character is denoted as a local shift of magnetic level, "L", a change of wave

amplitude, "A", or a change of wavelength (average horizontal distance between

magnetic peaks or troughs), "W". The letter "G" denotes a gradual change, such as

a gently dipping contact. Changes from short to long wavelength anomalies indicate

an increase in depth to underlying magnetic rocks, a decrease of large scale

heterogeneity of magnetization of the rocks, or an increase in lateral distance of

the sensor from nearby magnetic rocks due to change of road direction or

topography. Shorter wavelengths anomalies also can be observed along roads near

steel fences (Figure 8b) or over road fill that consists of crushed magnetic rock.

A decrease of wavelength results from increasing depth of magnetic rocks

beneath alluvium. Thus, a commonly-used estimate of the maximum thickness of

alluvium (depth to the top of magnetic rock) can be made by measuring the
4

horizontal extent of the steepest gradient associated with magnetic anomalies.

Magnetometer traverses in Warner Valley, however, provided only six locations

farther than a horizontal distance of one kilometer from Tertiary rock, where a

possible depth estimate could be made. Several maximum-depth-estimates can be made

near the edge of Warner Valley (at interpolated location numbers 15.3, 68.6, 73.5,

74.6, and 76.3) with the thickness of alluvium ranging to 500 feet and in Coleman

Valley (at location numbers 38.7, 39.8, and 40.2 in Figures 7 and 8b) with

thicknesses of less than 200 feet.

The entire length of traverse W1 (Figures 7 and 8a, and 11) along the main

highway across Warner Valley indicates the shortest wavelength background signal of

all traverses across Warner or Coleman Valleys. Perhaps much of high frequency

content can be related to man-made interference such as culverts, magnetic road

fill, power lines, and the steel reflector posts that occur at intervals of 0.1

mile. Except for Coleman Valley, the alluvium may be thinner along the highway

than at other valley locations. The occurrence of an audio-magnetotelluric high

near the highway also tends to indicate a minimum thickness of alluvium there. The

occurrence of step-like magnetic features, a major fault at the edge of the valley,

a general decrease of magnetic level to the west, and the absence of high amplitude

anomalies tend to indicate a large thickness of alluvium along the highway.

According to the amplitudes of magnetic anomalies recorded near the edge of and

outside Warner Valley, the Tertiary rocks are highly magnetic. One would expect

that the amplitude of magnetic anomalies caused by Tertiary rocks underlying thin

alluvial cover not to be greatly decreased. Short wavelength anomalies superimposed

on longer wavelength, higher amplitude anomalies such as near the west edge of

Coleman Valley (near location-point 39, Figure 8b) would be expected. But the

short wavelength anomalies along the highway, where depth estimates would be less

than 200 feet, are of relatively small amplitude (less than 100 gammas).

Therefore, if the alluvium is thin along the highway, the magnetization of the

underlying rock would be unusually low or, possibly, unusually homogeneous compared

to other Tertiary rock in the area.

Aeromagnetic survey

The aeromagnetic map (Figure 9) provides information to fill in the gaps of the

truck-mounted magnetometer survey and permits a view of the regional magnetic

background near the Crump Geyser area with less interference from local anomalies

than the ground level survey. The truckborne magnetometer survey, however,

provides more accurate locations and depth estimates. Note that not only are the

amplitudes of aeromagnetic anomalies smaller than the equivalent ground level

anomalies but, because of the inclination of the earth's field, the locations of

the aeromagnetic anomalies are shifted south 20 degrees west from the corresponding

ground locations. The amount of shift varies from about 440 feet at a 6000-foot

elevation to 1110 feet at a 4500-foot ground elevation.

The west edge of Warner Valley is marked by a series of prominent magnetic

highs and lows that are elongated nearly parallel to the trend of the boundary

escarpment. The map has been annotated to indicate which anomalies occur over the

Tts geologic unit (with the letter S) and over the Tbf unit (with the letter K).

The shape of the edges of the elongated anomalies are shifted in places to agree

with the trend of three pairs of northwest-trending faults, but this tendency does

not seem to persist into the overlying Tb to the west. The occurrence of a

prominent north-elongated, magnetic low may correlate with underlying reversely

magnetized rock or, possibly, may be related to a topographic effect. The letter T

in a southwest-trending low to the north of Deep Creek Canyon indicates a probable
5

topographic effect of the missing Tts and Tb rocks.

Several magnetic highs to the east of Warner Valley are related to outcrops of

the Tb geologic unit. Three lows, denoted by the letter R are related to reversely

polarized rocks of the Tb unit. The northeast and southwest edges of these

northwest-trending lows appear to be fault controlled.

Warner Valley appears to coincide with a general magnetic low. Decreases in

magnetic level and diversity of magnetic trends and a general increase in

wavelengths are partly effects of an average 1000 to 1500-foot lower ground surface

of the valley relative to the surrounding terrain. The occurrence of alluvium

above Tertiary bedrock in the valley also contributes to these changes. If it is

determined from other evidence that the alluvium is relatively thin, extensive

hydrothermal alteration serving to destroy magnetization of the rocks beneath

Warner Valley also may contribute to the reduced amplitude of the magnetic

anomalies.

The magnetic contours noticeably follow the trend of the edge of the alluvium

at the north edge of Warner Valley near two locations labeled with the letter Q.

It is unlikely that the closely-spaced northeast-trending contours northwest of the

eastern of the two locations only result from terminating a large block of

alluvium. The size of the gradient and persistence across an outcrop of Tertiary

rock (Tb) suggest that the low mostly is the effect of a thick block of relatively

non-magnetic Tertiary rock.

The letter F near the center of the aeromagnetic map indicates the position of

a mapped fault. The Tertiary rocks to the east are at a relatively low elevation

but also would seem to have relatively low magnetization. But ground traverse W6

(Figure 8d) which is located nearby indicates rocks of relatively high

magnetization. The difference of results would have to be explained by the 2300 to

2500-foot difference in observation level, the relatively small volume of rocks

involved, and incompleteness of the aeromagnetic coverage.

The aeromagnetic map is dominated by a 5 by 7 km magnetic high near the south

edge of Warner Valley (labeled P). The total amplitude of about 200 gammas is

larger than anomalies in the mountains to the west, but rocks causing the latter

anomalies are much closer to the flight elevation. The large high may be the

magnetic effect of an intrusive stock buried below sealevel. Magnetic lows labeled

C and D are partly the dipole effect of the large magnetic high.

GRAVITY SURVEY

The Bouguer gravity anomaly map of the Crump Geyser area is dominated by a 9 by

12 km closed gravity low (Figure 10). The gradient along the west edge of the

gravity low correlates with the fault at the west edge of Warner Valley and with a

similar magnetic gradient (Figure 9). Both the northeast-trending gravity and

magnetic contours curve eastward just south of Crump Geyser. The large magnetic

high near the south edge of the valley is reflected as a small divergence of the

gravity contour between the minus 72 and the minus 74 levels.

Gravity data were collected at station spacings of 250 to 350 feet along three

east-west profiles in Warner Valley in addition to gravity stations established for

regional control. The purpose of the closely-spaced stations was to provide better

resolution for the location of faults, to test for changes of density within the

alluvium, and to provide better control for two-dimensional interpretation.

Elevations were leveled to an overall accuracy of 0.05 foot and gravity was
6

observed to an accuracy of 0.05 milligal.

Profile A-A' crosses Warner Valley along the main highway (Figures 10 and 11)

and coincides with truckborne magnetometer traverses (W1 and W5 of Figures 8a and

8c). The gravity level is about five milligals lower on the east side of the

valley compared to the west side. The gravity gradient is steeper on the west side

of the valley, which would indicate that the alluvium is thicker near the west side

of the valley. Only one local anomaly appears on the profile. The shape of the

anomaly at point P tends to be the reverse of the shape of topography. Using a

reduction density of 2.0 g/cm3 for alluvium rather than the value of 2.5 g/cm3 for

volcanic rock halves the size of the anomaly. The remaining part of the anomaly

might be interpreted as the effect of being about 30 feet closer to bedrock in the

topographic low. The change west of P is opposite in sense to that on the

magnetometer record which implies a step fault down-dropped to the east.

Profile B-B'-B" also coincides with truckborne magnetometer traverses (W8 and

W9 of Figures 8e and 8f), but the elevation changes are insignificant. The gravity

gradient is the same as that of profile A-A' for the section from point P for 1.1

km to the east, but is steeper than to west of point P. A one-milligal gravity

high centered 1.24 km west of B' has about the same peak-to-trough wavelength as a

corresponding magnetic change.

Profile C-C' (Figure 13) was intended to establish the gravity gradient at the

west edge of Warner Valley near a location about as far north of Crump Geyser as BB'-B" is to the south. The gradient is smaller than at either of the other

surveyed profiles, indicating that the major fault is located farther to the west

of the edge of the alluvium or the throw is less.

Two-dimensional interpretation of the configuration of the valley floor beneath

the alluvium is most accurate if a profile is chosen at right angles to the strike

of the anomaly. None of the surveyed profiles meet this criterion. Therefore, an

arbitrary profile, D-D' (Figure 14), was selected that passes nearly through the

center of the gravity low, which corresponds to the location of the greatest

thickness of alluvium.

One would assume from the asymmetric appearance of the gravity map (Figure. 10)

and the gravity profiles (Figures 11, 12, and 14) that the thickest part of the

alluvium occurs near the west side of Warner Valley. But if the gravity low is

wholly attributed to the contrast in density between the alluvium and the

surrounding Tertiary rocks, one must assume the existence of a regional gravity

anomaly that coincides with the observed profile west of the west side of the

valley and rejoins the observed anomaly at a 13-milligal lower level near the east

edge of the valley where Tertiary rocks crop out. Consequently the residual

anomaly and the computed depth profile would be shaped fairly symmetrically (Figure

14). A maximum alluvium thickness of about 2700 feet (base about 1800 feet above

sea level) can be derived from the residual gravity anomaly, if the average density

of the alluvium is 2.0 g/cm3 compared to 2.5 g/cm3 for the underlying Tertiary

rocks.

The shape of the regional anomaly indicates that the fault zone near the west

edge of Warner Valley and south of Crump Geyser separates two units of rock beneath

the alluvium, in which the less dense unit is located to the east of the fault.

The relative flatness of the observed anomaly to the west of Warner Valley

indicates that the transition between the two units occurs over a fairly short

distance interval. The gravity survey should be carried to the east of the east

edge of Coleman Valley to determine the location of the east edge of the down-
7

dropped block of low density rock. Here the contact between the Tts and Tb rock

units is located at a comparable elevation (about 6000 feet) to the location of the

contact just west of Warner Valley.

If a greater part of the observed gravity anomaly is attributed to the contrast

in density between the underlying rocks, the alluvium would be correspondingly

thinner than illustrated in Figure 14. The audio-magnetotelluric survey was not

carried far enough south to evaluate the geothermal potential near the gravity low.

As stated in an earlier section of the report, the truckborne magnetic data show

very few locations where estimates of the maximum depth to the base of the alluvium

can be applied. The rock underlying the alluvium has a lower density than the

surrounding basement rocks and has a relatively low intensity of magnetization.
8

List of Figures

Fig. 1. Index and tectonic map of Crump Geyser area, Oregon (color version)

2. Geologic map of Crump Geyser area, Oregon

3. Apparent resistivity at 285 Hz

4. Apparent resistivity at 27 Hz, east electric component

5. Apparent resistivity at 27 Hz, north electric component

6. Apparent resistivity at 7.5 Hz

7. Location of truckborne magnetometer traverses

8a. Magnetometer traverse W1

8b. Magnetometer traverse W2

8c. Magnetometer traverses W3, W4, and W5

8d. Magnetometer traverses W6 and W7

8e. Magnetometer traverse W8

8f. Magnetometer traverses W9, W10, W11, and W12

9. Aeromagnetic map of KGRA, Warner Valley, Oregon

10. Bouguer gravity map of Crump Geyser area, Oregon

11. Gravity and magnetic anomalies along profile A-A'

12. Gravity and magnetic anomalies along profile B-B'-B"

13. Gravity anomaly along profile C-C'

14. Interpretation of gravity anomaly along profile D-D'


SYMBOLS USED I I 

ELEVATION CONTOUR NEAR â‚¬226 OF VALLEY 

8 19.1 

AMT STA-HOM AND VALUE 
SYMBOLS USED I 

/' 

E LEVAT~ON CONTOUR NUB EDGE OF VALLEY 

HACHURES OH LOW SIDE. INTERVAL /N 

OHMMET RES IS LOGARITHMIC. 

1 0 I 2 3 4 MILES 

1--.*1...-1 

1 0 I 2 3 4 5 KILOMETRES 

I I 
SYMBOLS USED I 

/' 


Figo 8a. Magnetometer traverse Wl 
Fig. 8b. Magnetometer traverse W2 
Fig. 8c. Magnetometer traverses W3, W4, and W5 
Fig. 8d. Magnetometer traverses W6 and W7 
Fig. 8e. Magnetometer traverse W8 
Fig. 8f. Magnetometer traverses W9, W10, Wll, and W12 


Fig. 11. Gravity and magnetic anomalies along profile A-A' 
Fig. 12. Gravity and magnetic anomalies along profile B-B'-B" 
0 Ã 2 3 4 MILES 

Fig. 13. Gravity anomaly along profile C-C' 
6000~---- ---- . true round _J 

5000 - +-< surfac-e. ---- --. - -- - - --------a 

- 

compwted depth - 

.^/ 2000 

- 

,QUOk Te-rfciary ro CK 

Mo verfcic-0.1 exci~~ge.rai.tt'on fl (WEST.) (EAST) 0' 

Fig, 14. Interpretation of gravity anomaly along profile D-D' 
APPENDIX 2—REPRINT OF NTIS PUBLICATION PB-245-426/AS

Gravity data in Crump Geyser area, Oregon

by

Donald Plouff

U. S. Geological Survey

Menlo Park, California

This report is preliminary and has

not been edited or reviewed for

conformity with Geological Survey

standards and nomenclature.
DESCRIPTION OF GRAVITY SURVEY

Gravity readings were taken with LaCoste-Romberg Meter G17B at 162

locations to obtain a Bouguer gravity anomaly map of the Crump Geyser

area (Plouff and Conradi, 1975, pl. 9). Gravity readings also were taken

at 194 locations at intervals of 70 to 120 meters along three traverses

(A-A', B-B', and C-C' on figure 1) to supplement the regional gravity

survey and to provide better resolution for interpretation of

near-surface gravity anomalies (Plouff and Conradi, 1975, pls. 10-12). The

gravity survey is located in an area of geothermal resource potential in

south central Oregon (fig. 1).

ACCURACY OF SURVEYED ELEVATIONS

The elevation control along the three traverses was carried to the

nearest 0.01 foot by using standard spirit leveling techniques. This

quality of elevation control made possible the determination that the

elevation of a U.S. Geological Survey benchmark on a bridge over Deep

Creek (1.5 mile east of Adel) has decreased 0.24 ± 0.02 foot since 1965

relative to benchmarks at distances of 0.4 and 0.6 miles on either side.

Ties between benchmarks along traverse A-A' indicates the surveyed

elevations probably are accurate to better than 0.05 foot. The absolute

elevation accuracy along traverse C-C' is not as good as along the other

two traverses because a tie was made to a spot elevation and a lake-level

elevation rather than to a benchmark. The relative accuracy along the

surveyed profiles, however, is significantly greater than the 0.2-foot

accuracy needed for consistency with the maximum reading accuracy of 0.01

milligal for Gravity Meter G17B.

1
OBSERVED GRAVITY

Absolute values of observed gravity were established by tying the

gravity readings to a primary base in Menlo Park, California (station 173),

which is incorporated in a network of base stations located throughout

California (Chapman, 1966, p. 36). Gravity readings also were taken at three

secondary bases of the California network and at a station in Klamath Falls,

Oregon, of the world relative gravity reference network (Jablonski, 1974). A

correction of 0.81 milligal was added to the observed gravity value at

Klamath Falls (Courthouse station ACIC 1300-2 or IGB 15721B) to account for a

nearly constant difference between gravity values of the two networks

(written communication, H.W. Oliver, 1975). The overall tide-corrected drift

curve indicates that the value determined for the base at Adel, Oregon is

tied to the station at Klamath Falls within an accuracy of about 0.05

milligal and is tied to the base at Menlo Park within an accuracy of about

0.08 milligal (fig. 2). Sudden local departures on the drift curve indicate

that observed gravity errors of 0.1 milligal could occur at non-repeated

gravity stations.

The observed gravity values at all stations in the Crump Geyser area

were tied to a local base at Adel, Oregon. The base reading was taken on a

small concrete slab that encloses the waste disposal trap at trailer site

number 5, located about 100 feet to the west of the Adel store and post

office. The gravity value there is 979,924.20 ± 0.08 milligals, as tied to

the California base network datum. Another base station was established in

case the above-described site is destroyed or is inaccessible. This station is

located at the northwest corner of a 3- by 7-foot concrete slab to the north

of the west door (to Post Office section) of the Adel store and is located

2
about 30 feet west southwest of the gas pumps. The gravity value there is

979,923.75 milligals, according to a gravity difference of 0.45 ± 0.02

milligal relative to the trailer site base. The locations of both base

stations are at 42° 10.59' north latitude and 119° 53.87' west longitude

and the elevations are about 4535 and 4538 feet above sea level,

respectively.

GRAVITY ANOMALIES

Principal facts, free-air anomalies, and complete Bouguer anomalies for

all the gravity stations established by the U.S. Geological Survey (fig. 1

and Plouff and Conradi, 1975, pl. 9) in the Crump Geyser area are listed in

this report (table 1). The prefix, W, for station names is used for

regional control stations and the prefixes WA, WB, and WC refer to stations

located along the three closely-spaced traverses. The four-digit code

associated with each gravity station can be used to describe the location

(table 2), estimate the elevation accuracy (table 3), estimate the accuracy

of horizontal location (table 4), and to estimate the accuracy of the

observed gravity (table 5).

Free-air gravity anomalies (table 1) were determined by using the

International Gravity Formula of 1930 for the normal gravity on the ellipsoid

and Swick's (1942, p. 65) formula for the free-air correction. Bouguer,

curvature, and terrain corrections were added to the free-air anomaly at each

station to determine complete Bouguer anomalies at reduction densities of 2.50

and 2.67 g/cm3. Hand terrain corrections, using conventional cylindrical

compartments, were estimated in the distance interval from the station

location to 0.9 km (2,936 feet). The terrain correction in the remaining

3
distance interval was determined in a computer program of Plouff (1966) by

using topography digitized in a 0.5-minute grid of average elevations to a

distance of 4.1 km, a one-minute grid to 10.5 km, and a three-minute grid to

a distance of 166.7 km. The terrain corrections listed in table 1 pertain

to an assumed rock density of 2.67 g/cm3.

ACKNOWLEDGMENTS

Arthur Conradi, Jr. and Nicholas E. Voeghtly assisted in the fieldwork.

REFERENCES

Chapman, R. H., 1966, Gravity base station network: California Div. Mines

and Geology Spec. Rept. 90 and Supplement, 53 p.

Jablonski, H. M., 1974, World relative gravity reference network North America,

Parts 1 and 2: DMAAC Ref. Pub. No. 25, orig. pub. 1970, revised 1974, about

1500 p.

Plouff, Donald, 1966, Digital terrain corrections based on geographic

coordinates [abs.]: Geophysics, v. 31, p. 1208.

Plouff, Donald, and Conradi, Arthur, Jr., 1975, Gravity and magnetic profiles

and maps, Crump Geyser area, Oregon: U.S. Geol. Survey open-file report

75-346, 2 p., 12 pls.

Swick, C. H., 1942, Pendulum gravity measurements and isostatic reductions:

U.S. Coast and Geod. Survey, Spec. Publ. 232, 82 p.

4
TABLE 1. PRINCIPAL FACTS AND GRAVITY ANOMALIES, CRUMP GEYSER AREA, OREGON.

OBSERVED FREE AIR TERRAIN BOUGUER ANOMALY

STATION CODE LATITUDE LONGITUDE ELEVATION GRAVITY ANOMALY HAND TOTAL 2.67 2.50

DEG MIN DEG MIN FEET MGAL MGAL MGAL MGAL

W 1 G534 42 9.99 119 50.19 4485.0 979926.40 -25.97 0.01 0.81 -179.47 -169.70

W 2 F534 42 9.52 119 50.19 4486.0 979924.25 -27.32 0.01 0.77 -180.89 -171.11

W 3 F534 42 9.13 119 50.19 4486.0 979922.89 -28.10 0.01 0.74 -181.70 -171.92

W 4 G534 42 8.87 119 50.48 4488.0 979922.26 -28.15 0.01 0.73 -181.84 -172.05

W 5 G534 42 8.64 119 51.33 4487.0 979921.35 -28.82 0.01 0.73 -182.46 -172.68

W 6 F534 42 9.09 119 51.31 4486.0 979921.72 -29.21 0.01 0.77 -182.78 -173.01

W 7 G534 42 9.52 119 51.03 4487.0 979923.39 -28.09 0.01 0.78 -181.68 -171.91

W 8 G534 42 9.98 119 51.02 4486.0 979924.30 -27.96 0.01 0.83 -181.47 -171.70

W 10 F534 42 12.00 119 49.12 4491.0 979934.70 -20.12 0.32 1.53 -173.10 -163.36

W 11 F534 42 12.38 119 48.50 4720.0 979922.13 -11.73 0.13 1.08 -173.00 -162.74

W 12 G644 42 11.37 119 48.23 5060.0 979895.09 -5.31 1.03 2.37 -176.93 -166.01

W 13 G644 42 10.46 119 47.58 5214.0 979883.00 -1.56 1.08 2.92 -177.90 -166.68

W 14 G634 42 10.46 119 46.75 5068.0 979896.74 -1.54 0.06 1.05 -174.76 -163.73

W 15 G634 42 10.98 119 46.64 5064.0 979897.18 -2.26 0.14 1.02 -175.38 -164.35

W 16 G633 42 15.04 119 46.59 4710.0 979930.33 -8.45 0.12 1.39 -169.07 -158.85

W 17 W534 42 14.90 119 45.91 4733.0 979928.62 -7.79 0.15 1.63 -168.96 -158.70

W 18 G634 42 12.90 119 45.14 4745.0 979922.64 -9.65 0.51 2.24 -170.62 -160.37

W 19 G533 42 15.55 119 47.15 4496.0 979945.04 -14.62 0.01 1.53 -167.77 -158.02

W 20 G534 42 16.46 119 46.84 4488.0 979947.31 -14.47 0.06 1.94 -166.94 -157.23

W 21 G534 42 16.11 119 47.14 4484.0 979946.70 -14.93 0.02 1.63 -167.57 -157.85

W 22 X524 42 18.74 119 47.32 4474.0 979950.49 -16.02 0.34 3.45 -166.50 -156.92

W 23 G634 42 13.86 119 48.17 4508.0 979940.19 -15.81 0.04 1.27 -169.64 -159.84

W 24 G644 42 13.53 119 49.55 4539.0 979936.83 -15.77 0.12 1.20 -170.73 -160.86

W 25 G534 42 10.84 119 50.18 4483.0 979929.12 -24.71 0.01 0.90 -178.05 -168.29

W 26 W554 42 11.74 119 50.17 4484.0 979932.08 -23.01 0.01 1.01 -176.27 -166.51

W 27 W534 42 12.94 119 50.58 4482.0 979934.55 -22.52 0.01 1.23 -175.50 -165.76

W 28 F534 42 9.78 119 54.07 4530.0 979919.97 -27.86 0.01 1.76 -181.95 -172.14

W 29 B124 42 9.20 119 54.93 4498.4 979922.04 -27.89 0.57 3.30 -179.37 -169.72

W 30 B124 42 9.09 119 53.48 4494.2 979916.53 -33.63 0.01 1.13 -187.13 -177.35

W 31 B124 42 9.08 119 52.02 4489.4 979919.57 -31.03 0.01 0.82 -184.67 -174.88

W 32 F534 42 8.64 119 51.94 4488.0 979919.41 -30.66 0.01 0.78 -184.29 -174.51

W 33 F534 42 7.97 119 51.86 4496.0 979918.64 -29.68 0.01 0.73 -183.64 -173.84

W 34 F534 42 8.02 119 53.09 4489.0 979914.78 -34.27 0.01 0.85 -187.86 -178.09

W 36 G534 42 5.44 119 54.59 4489.0 979917.04 -28.15 0.01 0.97 -181.63 -171.86

W 37 F534 42 4.65 119 54.36 4497.0 979917.46 -25.79 0.01 1.11 -179.40 -169.62

W 39 G534 42 7.34 119 54.40 4486.0 979916.17 -32.14 0.01 1.07 -185.42 -175.66

W 40 F534 42 7.78 119 54.42 4485.0 979915.17 -33.89 0.01 1.17 -187.03 -177.28

W 41 F534 42 8.22 119 54.31 4488.0 979914.39 -35.05 0.01 1.25 -188.22 -178.46

W 42 N324 42 8.64 119 55.89 4510.0 979923.53 -24.47 1.77 6.22 -173.42 -163.94

W 43 F534 42 7.78 119 56.24 4492.0 979923.84 -24.57 0.65 4.94 -174.18 -164.65

W 44 B124 42 5.91 119 57.04 4533.8 979925.52 -16.16 0.40 3.29 -166.84 -159.13

W 46 F534 42 4.43 119 57.72 4602.0 979921.77 -11.29 0.34 2.51 -167.10 -157.18

W 47 G634 42 3.10 119 58.12 4624.0 979917.54 -11.46 0.66 2.73 -167.80 -157,85

W 49 F534 42 10.84 119 51.03 4484.0 979927.49 -26.25 0.01 0.94 -179.58 -169.82

W 50 G534 42 11.90 119 51.17 4481.0 979930.24 -25.37 0.01 1.19 -178.35 -168.61

W 52 G534 42 9.08 119 54.25 4494.0 979917.49 -32.68 0.01 1.59 -185.71 -175.96

W 53 G534 42 9.08 119 53.07 4495.0 979916.67 -33.40 0.01 1.00 -187.05 -177.27

W 54 F534 42 8.65 119 53.08 4491.0 979915.39 -34.41 0.01 0.93 -187.99 -178.22

W 55 G534 42 8.02 119

119

53.69 4488.0 979914.20 -34.94 0.01 0.97 -188.38 -178,61

W 56 G534 42 9.96 119 52.62 4492.0 979921.16 -30.51 0.01 1.08 -183.98 -174.21

5
TABLE 1--CONTINUED

STATION CODE LATITUDE LONGITUDE ELEVATION

DEG MIN DEG MIN FEET

OBSERVED

GRAVITY

MGAL

FREE AIR

ANOMALY

MGAL

TERRAIN BOUGUER ANOMALY

HAND TOTAL 2.67 2.50

MGAL MGAL

W 57 G544 42 10.09 119 54.06 4558.0 979921.01 -24.65 0.01 1.88 -179.58 -169.71

W 58 N324 42 7.48 119 56.36 4509.0 979923.24 -23.12 1.05 4.96 -173.29 -163.72

W 59 G634 42 7:10 119 56.52 4489.0 979924.87 -22.80 0.45 4.14 -173.11 -163.54

W 60 N324 42 6.61 119 56.94 4512.0 979925.50 -19.28 1.36 5.31 -169.21 -159.66

W 61 G544 42 5.45 119 52.27 4496.0 979914.99 -29.55 0.09 0.98 -183.26 -173.47

W 62 G544 42 4.79 119 53.63 4489.0 979916.82 -27.39 0.03 1.07 -180.77 -171.00

W 63 G644 42 4.25 119 54.50 4501.0 979919.11 -23.17 0.24 1.63 -176.40 -166.64

W 64 G634 42 4.20 119 55.08 4525.0 _ 979920.06 -19.89 0.27 1.71 -173.85 -164.05

W 65 G634 42 3.48 119 55.35 4883.0 979899.22 -6.00 0.21 0.98 -172.96 -162.33

W 66 G634 42 3.78 119 56.20 5029.0 979889.59 -2.96 0.01 0.68 -174.61 -163.65

W 67 G634 42 3.08 119 56.71 5191.0 979879.22 3.54 0.01 0.64 -174.30 -162.98

W 68 G634 42 2.70 119 56.17 5124.0 979884.29 2.88 0.03 0.57 -172.74 -161.56

W 69 G644 42 1.47 119 55.30 5422.0 979864.18 12.62 0.04 0.64 -173.12 -161.30

W 70 G634 42 0.59 119 53.25 6047.0 979818.92 27.41 0.19 2.07 -178.26 -165.16

W 71 X524 42 1.13 119 53.19 5786.0 979836.24 19.40 0.17 1.37 -178.05 -165.48

W 72 F534 42 1.80 119 52.59 5410.0 979857.66 4.48 0.17 1.06 -180.43 -168.65

W 73 G644 42 2.82 119 52.36 5122.0 979877.08 -4.69 0.10 0.92 -179.89 -168.73

W 74 F544 42 3.65 119 51.22 5014.0 979883.97 -9.19 0.14 1.03 -180.58 -169.67

W 75 F534 42 2.52 119 50.13 4529.0 979916.53 -20.53 0.06 1.66 -174.68 -164.87

W 76 B124 42 2.68 119 49.36 4468.7 979917.80 -25.17 0.01 1.31 -177.61 -167.90

W 77 B124 42 2.64 119 48.06 4466.7 979916.25 -26.85 0.01 1.38 -179.15 -169.45

W 78 B124 42 2.01 119 47.49 4477.8 979914.75 -26.36 0.01 1.74 -178.68 -168.99

W 79 B124 42 1.24 119 47.17 4493.9 979912.27 -26.17 0.01 2.06 -178.73 -169.02

W 80 B124 42 0.43 119 46.81 4531.0 979907.61 -26.14 0.01 2.36 -179.67 -169.89

W 81 B124 42 3.34 119 50.20 4508.1 979917.69 -22.56 0.48 1.81 -175.85 -166.09

W 82 N224 42 4.11 119 50.41 4490.1 979919.05 -24.05 0.84 1.98 -176.55 -166.84

W 83 B124 42 5.59 119 50.32 4561.4 979914.48 -24.13 0.11 0.84 -180.22 -170.28

W 84 B124 42 6.39 119 50.32 4584.0 979913.23 -24.45 0.04 0.69 -181.46 -171.46

W 85 N224 42 7.12 119 50.99 4508.2 979918.59 -27.31 0.33 1.03 -181.38 -171.57

W 86 B124 42 18.98 119 52.91 4583.6 979946.43 -10.14 0.25 3.35 -164.48 -154.65

W 87 N224 42 19.59 119 53.12 4628.0 979945.65 -7.66 0.16 2.38 -164.49 -154.50

W 88 B124 42 19.95 119 53.23 4679.1 979943.54 -5.50 0.09 1.92 -164.54 -154.41

W 89 B124 42 20.56 119 53.39 4657.2 979947.63 -4.38 0.04 1.71 -162.88 -152.79

W 90 B124 42 21.32 119 53.83 4584.9 979952.53 -7.42 0.01 1.82 -163.33 -153.40

W 91 F534 42 22.39 119 53.32 4477.0 979958.44 -13.25 0.07 1.64 -165.64 -155.94

W 92 W534 42 22.12 119 52.51 4474.0 979961.52 -10.05 0.16 1.79 -162.19 -152.50

W 93 W544 42 21.63 119 51.96 4474.0 979961.79 -9.04 0.12 1.89 -161.08 -151.40

W 94 W544 42 20.88 119 51.21 4474.0 979958.60 -11.11 0.16 2.09 -162.95 -153.28

W 95 W534 42 21.28 119 50.36 4474.0 979959.77 -10.54 0.12 2.60 -161.87 -152.23

W 96 W544 42 20.48 119 50.39 4475.0 979956.14 -12.88 0.42 2.52 -164.32 -154.68

W 97 W554 42 19.98 119 49.87 4476.0 979953.89 -14.29 0.60 2.67 -165.62 -155.98

W 98 N224 42 22.29 119 54.42 4491.8 979955.95 -14.20 0.70 2.88 -165.85 -156.21

W 99 B124 42 23.40 119 54.51 4484.6 979959.18 -13.31 1.23 3.17 -164.43 -154.81

W 100 B123 42 24.48 119 54.51 4511.5 979962.04 -9.54 0.16 1.67 -163.09 -153.31

W 101 G634 42 24.61 119 57.12 5109.0 979923.55 7.93 0.01 0.83 -166.92 -155.78

W 102 F534 42 24.21 119 57.70 5206.0 979917.36 11.46 0.01 0.80 -166.74 -155.39

W 103 G644 42 23.33 119 59.10 5324.0 979908.85 15.36 0.01 0.73 -166.94 -155.33

W 104 F534 42 22.58 119 59.44 5414.0 979901.81 17.90 0.01 0.74 -167.47 -155.67

W 105 F534 42 22.24 119 59.63 5443.0 979900.21 19.53 0.01 0.74 -166.83 -154.96

W 106 F534 42 21.68 119 59.32 5482.0 979897.91 21.74 0.01 0.77 -165.93 -153.98

6
TABLE 1—CONTINUED

STATION CODE LATITUDE LONGITUDE ELEVATION GRAVITY ANOMALY HAND TOTAL 2.67 2.50

DEG MIN DEG MINGRAVIFTEYET ANOMALY HAND TOTAL 2.67 2.50

OBSERVED

GRAVITY

MGAL

FREE AIR

ANOMALY

MGAL

TERRAIN

HAND TOTAL

MGAL

BOUGUER ANOMALY

2.67 2.50

MGAL

W 107 F534 42 19.61 119 57.41 5648.0 979882.99 25.52 0.17 1.24 -167.35 -155.07

W 108 F534 42 21.54 120 0.14 5530.0 979893.73 22.28 0.01 0.76 -167.03 -154.98

W 109 G634 42 20.53 120 1.01 5631.0 979883.33 22.88 0.01 0.81 -169.83 -157.56

W 110 B224 42 19.94 120 1.75 5713.0 979877.43 25.57 0.02 0.92 -169.84 -157.40

W 111 G634 42 18.77 120 2.47 5763.0 979871.32 25.91 0.01 1.08 -171.05 -158.51

W 112 G634 42 17.15 120 4.20 5661.0 979874.00 21.43 0.02 1.16 -171.96 -159.65

W 113 B124 42 12.89 120 4.88 5454.8 979880.98 15.41 0.26 1.00 -171.09 -159.22

W 114 B124 42 26.64 119 49.06 4477.3 979955.67 -22.36 0.06 4.92 -171.49 -161.99

W 115 B224 42 26.67 119 50.00 4473.3 979956.49 -21.96 0.01 2.94 -172.92 -163.31

W 116 B124 42 26.74 119 51.30 4476.2 979961.97 -16.31 0.01 1.83 -168.49 -158.80

W 117 B124 42 26.37 119 53.06 4474.1 979969.24 -8.69 0.01 1.32 -161.31 -151.59

W 118 B224 42 25.50 119 53.08 4490.9 979964.03 -11.01 0.01 1.33 -164.19 -154.43

W 119 B124 42 25.27 119 54.27 4514.5 979963.47 -9.01 0.01 1.27 -163.06 -153.25

W 120 G644 42 19.64 119 54.22 4753.0 979936.40 -5.23 0.39 3.78 -164.94 -154.77

W 121 G644 42 19.96 119 52.38 4781.0 979938.05 -1.43 0.10 1.50 -164.38 -154.00

W 122 G644 42 19.34 119 52.22 4532.0 979950.57 -11.38 0.36 2.44 -164.86 -155.09

W 123 G534 42 19.00 119 52.26 4482.0 979953.01 -13.13 0.06 2.51 -164.82 -155.17

W 124 X524 42 18.73 119 51.38 4479.0 979950.51 -15.51 0.17 2.10 -167.51 -157.84

W 125 W534 42 18.50 119 50.79 4479.0 979949.25 -16.43 0.23 1.91 -168.62 -158.93

W 126 W544 42 18.68 119 50.34 4478.0 979950.85 -15.19 0.17 1.82 -167.44 -157.75

W 127 N324 42 17.93 119 52.37 4501.1 979944.49 -18.26 0.36 4.17 -168.95 -159.36

W 128 D434 42 17.22 119 52.01 4489.0 979944.77 -18.05 1.06 4.11 -168.39 -158.82

W 129 B124 42 16.47 119 51.83 4481.9 979945.09 -17.27 0.23 3.02 -168.45 -158.82

W 130 R324 42 16.06 119 52.55 4481.0 979942.07 -19.77 0.58 6.50 -167.44 -158.04

W 131 B124 42 14.93 119 52.47 4496.8 979939.86 -18.80 0.39 5.94 -167.57 -158.10

W 132 B124 42 11.46 119 53.88 4630.8 979922.13 -18.74 0.47 4.29 -173.75 -163.88

W 133 B124 42 12.27 119 53.51 4551.3 979929.66 -19.89 0.70 5.84 -170.63 -161.03

W 134 B124 42 13.06 119 52.77 4534.1 979933.08 -19.27 0.23 4.10 -171.16 -161.49

W 135 B124 42 14.03 119 52.71 4516.1 979936.96 -18.54 0.60 5.94 -167.97 -158.46

W 136 G644 42 20.38 119 47.44 4532.0 979947.21 -16.30 0.88 6.33 -165.89 -156.37

W 137 X524 42 19.14 119 47.48 4477.0 979948.43 -18.39 0.25 3.54 -168.89 -159.31

W 138 G644 42 13.73 119 44.71 4946.0 979910.92 -3.72 0.20 1.69 -172.12 -161.40

W 139 G634 42 12.15 119 44.09 5274.0 979886.61 5.16 0.08 1.24 -174.92 -163.46

W 140 F534 42 11.53 119 43.72 5348.0 979880.04 6.47 0.02 1.16 -176.22 -164.59

W 141 W534 42 12.64 119 42.80 5380.0 979880.71 8.49 0.02 1.38 -175.07 -163.38

W 142 G634 42 13.48 119 42.50 5411.0 919882.55 11.99 0.53 2.25 -171.77 -160.07

W 143 G644 42 14.91 119 42.61 5480.0 979882.33 16.11 0.38 2.06 -170.19 -158.33

W 144 X624 42 15.25 119 43.01 5352.0 979890.06 11.30 0.64 2.45 -170.23 -158.68

W 145 G634 42 10.57 119 44.09 5121.0 979895.40 1.94 0.11 1.46 -172.68 -161.56

W 146 G744 42 9.66 119 44.39 5223.0 979887.31 4.79 0.38 1.78 -173.00 -161.68

W 147 B124 42 7.36 119 46.47 4567.2 979920.37 -20.34 0.02 1.29 -176.18 -166.26

W 148 B124 42 9.76 119 47.74 4494.7 979928.84 -22.28 0.02 1.28 -175.64 -165.88

W 149 B124 42 8.93 119 47.38 4513.0 979925.84 -22.31 0.01 1.11 -176.47 -166.65

W 150 B124 42 8.09 119 46.93 4534.6 979923.27 -21.60 0.01 1.14 -176.47 -166.61

W 151 F534 42 6.33 119 46.76 4605.0 979917.55 -18.07 0.14 1.26 -175.23 -165.23

W 152 F534 42 5.56 119 46.83 4509.0 979921.58 -21.91 0.03 1.41 -175.63 -165.84

W 153 F534 42 4.09 119 46.47 4500.0 979919.72 -22.41 0.02 2.09 -175.15 -165.42

W 154 G534 42 3.32 119 46.49 4484.0 979918.50 -23.99 0.02 2.49 -175.78 -166.11

W 155 F534 42 5.74 119 56.50 4504.0 979922.05 -22.18 0.01 1.87 -175.27 -165.52

W 156 G634 42 2.00 119 59.25 4954.0 979895.23 -1.11 0.41 1.67 -169.81 -159.07

7
TABLE 1--CONTINUE

STATION CODE LATITUDE LONGITUDE ELEVATION

DEG MIN DEG MIN FEET

OBSERVED

GRAVITY

MGAL

FREE AIR

ANOMALY

MGAL

TERRAIN

HAND TOTAL

MGAL

BOUGUER ANOMALY

2.67 2.50

MGAL

W 157 G634 42 1.19 119 58.30 5276.0 979873.52 8.66 0.09 0.67 -172.06 -160.55

W 158 N324 42 1.64 119 59.87 5230.0 979878.20 8.34 0.31 1.20 -170.27 -158.90

W 159 N224 42 0.68 120 0.55 5544.0 979858.97 20.06 -0.07 0.76 -169.73 -157.65

W 160 N224 42 2.51 120 1.22 5774.0 979847.22 27.19 0.26 1.20 -170.03 -157.47

W 161 B124 42 3.09 120 1.84 5745.2 979850.39 26.78 0.03 0.81 -169.84 -157.32

W 162 F534 42 9.35 119 48.30 4487.0 979926.86 -24.37 0.01 0.94 -177.81 -168.04

W 163 G534 42 8.22 119 48.91 4486.0 979923.56 -26.07 0.01 0.78 -179.63 -169.85

W 164 B124 42 10.54 119 56.02

.

4746.7 979916.39 -12.21 2.75 7.30 -168.18 -158.25

W 165 N434 42 10.49 119 57.22 4898.0 979908.32 -5.98 1.28 4.46 -169.98 -159.53

W 166 B124 42 10.89 119 58.29 4955.1 979904.40 -5.14 0.54 3.31 -172.24 -161.60

W 167 N224 42 11.11 119 59.41 4963.4 979904.38 -4.70 2.69 5.24 -170.15 -159.61

W 168 N324 42 12.53 120 1.97 5224.0 979893.28 6.56 0.33 1.37 -171.67 -160.33

W 169 B124 42 13.00 120 2.90 5296.7 979888.90 8.31 0.62 1.54 -172.24 -160.75

WA 1 B122 42 10.47 119 51.67 4485.9 979924.20 -28.81 0.01 0.97 -182.18 -172.41

WA 2 P124 42 10.47 119 51.74 4486.6 979925.13 -27.81 0.01 0.99 -181.19 -171.42

WA 3 P124 42 10.47 119 51.80 4486.9 979924.96 -27.95 0.01 1.00 -181.33 -171.56

WA 4 P124 42 10.47 119 51.88 4486.7 979924.79 -28.14 0.01 1.01 -181.49 -171.73

WA 5 P124 42 10.47 119 51.93 4487.9 979924.54 -28.28 0.01 1.02 -181.66 -171.90

WA 6 P124 42 10.47 119 51.99 4490.1 979924.20 -28.41 0.01 1.03 -181.86 -172.09

WA 7 P124 42 10.47 119 52.06 4492.6 979923.90 -28.48 0.01 1.05 -182.00 -172.23

WA 8 P124 42 10.48 119 52.14 4494.8 979923.54 -28.64 0.01 1.08 -182.21 -172.43

WA 9 B122 42 10.49 119 52.21 4495.7 979923.35 -28.76 0.01 1.10 -182.34 -172.56

WA 10 P124 42 10.47 119 51.59 4486.8 979925.39 -27.53 0.01 0.96 -180.94 -171.17

WA 11 P124 42 10.47 119 51.52 4487.2 979925.58 -27.31 0.01 0.95 -180.75 -170.98

WA 12 P124 42 10.47 119 51.46 4487.1 979925.72 -27.17 0.01 0.94 -180.61 -170.84

WA 13 P124 42 10.47 119 51.39 4487.3 979925.90 -26.98 0.01 0.93 -180.44 -170.67

WA 14 P124 42 10.47 119 51.32 4486.8 979926.02 -26.90 0.01 0.92 -180.35 -170.58

WA 15 P124 42 10.47 119 51.25 4486.8 979926.08 -26.84 0.01 0.91 -180.30 -170.53

WA 16 P124 42 10.47 119 51.17 4486.8 979926.15 -26.77 0.01 0.90 -180.24 -170.47

WA 17 P124 42 10.47 119 51.10 4486.8 979926.29 -26.63 0.01 0.89 -180.11 -170.33

WA 18 P123 42 10.47 119 51.03 4486.7 979926.40 -26.53 0.01 0.89 -180.01 -170.24

WA 19 P124 42 10.47 119 50.98 4487.0 979926.48 -26.42 0.01 0.88 -179.91 -170.14

WA 20 P124 42 10.47 119 50.91 4486.8 979926.64 -26.28 0.01 0.88 -179.77 -170.00

WA 21 P124 42 10.47 119 50.83 4487.4 979926.78 -26.09 0.01 0.87 -179.61 -169.84

WA 22 P124 42 10.47 119 50.76 4486.7 979926.99 -25.94 0.01 0.87 -179.44 -169.67

WA 23 P124 42 10.47 119 50.70 4487.4 979927.03 -25.84 0.01 0.86 -179.37 -169.59

WA 24 P124 42 10.47 119 50.63 4486.9 979927.24 -25.67 0.01 0.86 -179.18 -169.41

WA 25 P124 42 10.47 119 50.58 4486.8 979927.31 -25.61 0.01 0.86 -179.12 -169.35

WA 26 B123 42 10.48 119 50.52 4483.2 979927.64 -25.64 0.01 0.86 -179.02 -169.26

WA 27 P124 42 10.47 119 50.46 4486.9 979927.46 -25.45 0.01 0.85 -178.98 -169.20

WA 28 P124 42 10.47 119 50.40 4487.2 979927.64 -25.25 0.01 0.85 -178.78 -169.00

WA 29 P124 42 10.47 119 50.34 4486.9 979927.74 -25.17 0.01 0.85 -178.69 -168.92

WA 30 P124 42 10.47 119 50.29 4487.0 979927.86 -25.04 0.01 0.85 -178.56 -168.79

WA 31 P124 42 10.47 119 50.23 4486.9 979927.96 -24.95 0.01 0.85 -178.47 -168.70

WA 32 P124 42 10.47 119 50.17 4486.8 979928.10 -24.82 0.01 0.85 -178.34 -168.56

WA 33 P124 42 10.47 119 50.11 4486.8 979928.23 -24.69 0.01 0.85 -178.21 -168.43

WA 34 P124 42 10.47 119 50.05 4486.6 979928.40 -24.54 0.01 0.86 -178.05 -168.27

WA 35 P124 42 10.47 119 49.99 4486.8 979928.48 -24.44 0.01 0.86 -177.95 -168.18

WA 36 P124 42 10.47 119 49.93 4486.9 979928.59 -24.32 0.01 0.86 -177.83 -168.06

WA 37 P124 42 10.48 119 49.87 4486.9 979928.70 -24.23 0.01 0.87 -177.74 -167.96

. 

8
TABLE 1--CONTINUED

STATION CODE LATITUDE LONGITUDE ELEVATION

DEG MIN DEG MIN FEET

OBSERVED

GRAVITY

MGAL

FREE AIR

ANOMALY

MGAL

TERRAIN

HAND TOTAL

MGAL

BOUGUER ANOMALY

2.67 2.50

MGAL

WA 38 P124 42 10.48 119 49.82 4486.8 979928.79 -24.15 0.01 0.87 -177.65 -167.88

WA 39 P124 42 10.48 119 49.76 4486.8 979928.90 -24.04 0.01 0.87 -177.54 -167.76

WA 40 P124 42 10.45 119 49.70 4486.9 979928.94 -23.99 0.01 0.88 -177.48 -167.71

WA 41 P124 42 10.48 119 49.64 4487.1 979929.05 -23.86 0.01 0.89 -177.36 -167.58

WA 42 P124 42 10.48 119 49.58 4487.0 979929.18 -23.74 0.01 0.89 -177.23 -167.45

WA 43 P124 42 10.48 119 49.52 4487.0 979929.20 -23.72 0.01 0.90 -177.20 -167.43

WA 44 P124 42 10.48 119 49.47 4487.0 979929.18 -23.74 0.01 0.90 -177.21 -167.44

WA 45 P124 42 10.48 119 49.41 4487.1 979929.18 -23.73 0.01 0.91 -177.20 -167.43

WA 46 P124 42 10.48 119 49.33 4486.8 979929.19 -23.75 0.01 0.92 -177.20 -167.83

WA 47 P124 42 10.48 119 49.28 4485.2 979929.37 -23.72 0.01 0.93 -177.10 -167.34

WA 48 P124 42 10.48 119 49.22 4486.5 979929.30 -23.66 0.01 0.94 -177.08 -167.31

WA 49 P124 42 10.48 119 49.17 4486.4 979929.40 -23.57 0.01 0.96 -176.97 -167.20

WA 50 P124 42 10.48 119 49.10 4486.6 979929.48 -23.48 0.01 0.96 -176.88 -167.11

WA 51 P124 42 10.48 119 49.04 4486.6 979929.59 -23.37 0.01 0.92 -176.82 -167.05

WA 52 P124 42 10.48 119 48.99 4486.7 979929.59 -23.36 0.01 0.99 -176.73 -166.97

WA 53 P124 42 10.48 119 48.93 4486.6 979929.52 -23.44 0.01 1.01 -176.79 -167.03

WA 54 P124 42 10.48 119 48.87 4487.5 979929.36 -23.51 0.01 1.03 -176.87 -167.11

WA 55 P124 42 10.48 119 48.81 4488.7 979929.26 -23.50 0.01 1.06 -176.88 -167.11

WA 56 P124 42 10.48 119 48.75 4489.8 979929.25 -23.40 0.01 1.08 -176.79 -167.03

WA 57 P124 42 10.48 119 48.69 4491.1 979929.23 -23.30 0.01 1.11 -176.71 -166.94

WA 58 P124 42 10.48 119 48.62 4491.5 979929.30 -23.19 0.01 1.15 -176.57 -166.81

WA 59 P124 42 10.48 119 48.56 4491.8 979929.42 -23.05 0.01 1.18 -176.41 -166.65

WA 60 P124 42 10.48 119 48.50 4491.6 979929.54 -22.95 0.01 1.22 -176.27 -166.51

WA 61 P124 42 10.48 119 48.44 4491.5 979929.68 -22.81 0.03 1.27 -176.07 -166.31

WA 62 P124 42 10.48 119 48.39 4491.5 979929.86 -22.63 0.06 1.33 -175.83 -166.07

WA 63 P124 42 10.48 119 48.32 4491.5 979930.06 -22.43 0.14 1.46 -175.51 -165.76

WA 64 P124 42 10.46 119 48.26 4491.5 979930.26 -22.21 0.31 1.65 -175.09 -165.36

WA 65 P124 42 10.44 119 48.21 4491.7 979930.40 -22.02 0.40 1.76 -174.80 -165.07

WA 66 P124 42 10.43 119 48.17 4493.6 979930.48 -21.74 0.48 1.85 -174.49 -164.77

WA 67 B122 42 10.43 119 48.12 4490.6 979930.92 -21.59 0.57 2.01 -174.08 -164.37

WA 68 P124 42 10.50 119 52.27 4496.3 979923.26 -28.81 0.01 1.12 -182.39 -172.61

WA 69 P124 42 10.51 119 52.33 4498.0 979923.07 -28.86 0.01 1.14 -182.48 -172.70

WA 70 P124 42 10.52 119 52.40 4499.2 979922.93 -28.90 0.01 1.16 -182.53 -172.75

WA 71 P124 42 10.52 119 52.46 4500.6 979922.84 -28.86 0.01 1.18 -182.52 -172.74

WA 72 P124 42 10.55 119 52.51 4502.0 979922.69 -28.92 0.01 1.21 -182.61 -172.82

WA 73 P124 42 10.56 119 52.57 4503.4 979922.59 -28.91 0.01 1.23 -182.62 -172.83

WA 74 P124 42 10.57 119 52.62 4504.7 979922.49 -28.90 0.01 1.25 -182.63 -172.84

WA 75 P124 42 10.58 119 52.68 4508.1 979922.27 -28.82 0.01 1.28 -182.64 -172.85

WA 76 P124 42 10.59 119 52.74 4513.6 979921.86 -28.72 0.02 1.31 -182.70 -172.90

WA 78 B124 42 10.60 119 52.80 4522.0 979921.27 -28.54 0.03 1.34 -182.78 -172.96

WA 79

P124

P124 42 10.61 119 52.82 4525.9 979921.09 -28.37 0.02 1.34 -182.74 -172.91

WA 80 P124 42 10.62 119 52.90 4535.6 979920.48 -28.08 0.02 1.37 -182.75 -172.91

WA 81 P124 42 10.62 119 52.93 4540.5 979920.15 -27.95 0.02 1.38 -182.78 -172.93

WA 82 P124 42 10.63 119 52.98 4547.2 979919.81 -27.67 0.07 1.45 -182.66 -172.79

WA 83 P124 42 10.64 119 53.02 4552.3 979919.53 -27.49 0.07 1.47 -182.64 -172.76

WA 84 P124 42 10.65 119 53.07 4558.2 979919.21 -27.27 0.07 1.50 -182.59 -172.70

WA 85 P124 42 10.65 119 53.11 4563.4 979918.97 -27.02 0.04 1.48 -182.53 -172.63

WA 86 P124 42 10.65 119 53.18 4567.0 979918.91 -26.74 0.05 1.54 -182.32 -172.42

WA 87 P124 42 10.65 119 53.23 4568.9 979918.97 -26.50 0.04 1.56 -182.13 -172.22

WA 88 P124 42 10.65 119 53.29 4569.8 979919.08 -26.31 0.05 1.61 -181.91 -172.01

9
TABLE 1—CONTINUED

FREE AIR TERRAIN BOUGUER ANOMALY

STATION CODE LATITUDE LONGITUDE ELEVATION

DEG MIN DEG MIN FEET

OBSERVED

GRAVITY

MGAL

ANOMALY

MGAL

HAND TOTAL

MGAL

2.67 2.50

MGAL

WA 89 P124 42 10.65 119 53.35 4570.1 979919.26 -26.10 0.02 1.63 -181.70 -171.79

WA 90 P124 42 10.65 119 53.40 4570.6 979919.48 -25.83 0.02 1.67 -181.41 -171.50

WA 91 P124 42 10.65 119 53.46 4570.6 979919.73 -25.58 0.01 1.71 -181.11 -171.21

WA 92 P124 42 10.65 119 53.51 4571.0 979919.93 -25.35 0.01 1.75 -180.85 -170.95

WA 93 P124 42 10.65 119 53.57 4571.2 979920.17 -25.09 0.03 1.83 -180.52 -170.62

WA 94 P124 42 10.65 119 53.62 4569.2 979920.54 -24.91 0.05 1.91 -180.19 -170.30

WA 95 P124 42 10.65 119 53.68 4564.4 979921.11 -24.79 0.03 1.97 -179.85 -169.98

WA 96 P124 42 10.65 119 53.73 4559.9 979921.70 -24.62 0.02 2.03 -179.46 -169.60

WA 97 P124 42 10.65 119 53.78 4553.7 979922.46 -24.44 0.02 2.12 -178.98 -169.14

WA 98 P124 42 10.65 119 53.82 4548.8 979923.10 -24.26 0.02 2.19 -178.56 -168.74

WA 99 P123 42 10.66 119 53.88 4542.8 979924.11 -23.83 0.02 2.32 -177.80 -168.00

WA100 P124 42 10.65 119 53.95 4545.8 979924.23 -23.42 0.02 2.41 -177.40 -167.60

WA101 P124 42 10.65 119 54.00 4550.9 979924.14 -23.03 0.02 2.49 -177.11 -167.30

WA102 P124 42 10.65 119 54.06 4560.1 979923.70 -22.60 0.03 2.58 -176.91 -167.08

WA103 P124 42 10.65 119 54.10 4565.3 979923.46 -22.35 0.08 2.68 -176.73 -166.90

WA104 P124 42 10.65 119 54.14 4570.0 979923.34 -22.03 0.07 2.73 -176.52 -166.68

WA105 P124 42 10.65 119 54.19 4572.7 979923.56 -21.56 0.05 2.80 -176.07 -166.23

WA106 P124 42 10.65 119 54.26 4574.0 979923.98 -21.01 0.09 2.99 -175.38 -165.55

WA107 P124 42 10.65 119 54.32 4575.4 979924.43 -20.43 0.13 3.16 -174.68 -164.86

WA108 P124 42 10.65 119 54.37 4578.7 979924.68 -19.87 0.18 3.30 -174.09 -164.27

WA109 P124 42 10.65 119 54.40 4582.7 979924.66 -19.52 0.22 3.40 -173.78 -163.96

WA110 P124 42 10.65 119 54.45 4590.5 979924.52 -18.92 0.25 3.51 -173.34 -163.50

WA111 P124 42 10.65 119 54.48 4595.6 979924.39 -18.57 0.40 3.70 -172.96 -163.13

WA112 P124 42 10.65 119 54.53 4607.2 979923.93 -17.94 0.39 3.75 -172.68 -162.83

WA113 P124 42 10.65 119 54.56 4612.4 979923.71 -17.68 0.48 3.89 -172.47 -162.61

WA114 P124 42 10.65 119 54.60 4619.0 979923.47 -17.30 0.56 4.03 -172.17 -162.31

WA115 P124 42 10.65 119 54.64 4624.2 979923.35 -16.93 0.68 4.21 -171.79 -161.93

WA116 P124 42 10.64 119 54.68 4628.6 979923.14 -16.71 0.89 4.46 -171.47 -161.62

WB 1 P124 42 6.86 119 56.75 4492.0 979925.59 -21.44 0.46 4.40 -171.59 -162.03

WB 2 P124 42 6.85 119 56.67 4491.6 979924.61 -22.44 0.21 3.84 -173.13 -163.54

WB 3 P124 42 6.85 119 56.57 4491.3 979923.61 -23.47 0.09 3.39 -174.60 -164.98

WB 4 P124 42 6.84 119 56.49 4490.4 979922.68 -24.47 0.04 3.09 -175.87 -166.23

WB 5 P124 42 6.84 119 56.42 4491.2 979921.84 -25.24 0.01 2.87 -176.89 -167.24

WB 6 P124 42 6.84 119 56.33. 4491.1 979921.01 -26.08 0.01 2.64 -177.96 -168.29

WB 7 P124 42 6.84 119 56.26 4490.8 979920.43 -26.68 0.01 2.48 -178.71 -169.03

WB 8 P124 42 6.84 119 56.18 4490.8 979919.92 -27.19 0.01 2.31 -179.38 -169.69

WB 9 P424 42 6.84 119 56.11 4491.1 979919.37 -27.72 0.01 2.19 -180.05 -170.35

WB 10 P124 42 6.84 119 56.03 4490.6 979918.93 -28.20 0.01 2.06 -180.64 -170.93

WB 11 P124 42 6.84 119 55.96 4490.6 979918.63 -28.50 0.01 1.96 -181.04 -171.33

WB 12 P124 42 6.84 119 55.91 4490.8 979918.40 -28.71 0.01 1.89 -181.32 -171.61

WB 13 P124 42 6.83 119 55.84 4489.8 979918.22 -28.97 0.01 1.81 -181.64 -171.92

WB 14 P124 42 6.83 119 55.78 4489.8 979918.02 -29.17 0.01 1.74 -181.91 -172.18

WB 15 P124 42 6.83 119 55.71 4489.1 979917.92 -29.34 0.01 1.67 -182.12 -172.40

WB 16 P124 42 6.83 119 55.66 4489.2 979917.80 -29.45 0.01 1.62 -182.28 -172.55

WB 17 P124 42 6.83 119 55.61 4490.0 979917.66 -29.51 0.01 1.57 -182.42 -172.69

WB 18 P124 42 6.83 119 55.56 4490.0 979917.62 -29.55 0.01 1.52 -182.51 -172.77

WB 19 P124 42 6.83 119 55.49 4490.1 979917.65 -29.52 0.01 1.47 -182.53 -172.79

WB 20 P124 42 6.83 119 55.43 4490.2 979917.70 -29.46 0.01 1.43 -182.52 -172.77

WB 21 P124 42 6.83 119 55.36 4489.6 979917.82 -29.39 0.01 1.39 -182.47 -172.72

WB 22 P124 42 6.83 119 55.31 4489.6 979917.96 -29.25 0.01 1.35 -182.36 -172.61

10
TABLE 1--CONTINUED

OBSERVED FREE AIR TERRAIN BOUGUER ANOMALY

STATION CODE LATITUDE LONGITUDE ELEVATION

DEG MIN DEG MIN FEET

GRAVITY ANOMALY HAND TOTAL

MGAL MGAL MGAL

2.67 2.50

MGAL

WB 23

29

24

W8

25

30

WB

26

31

27

WB

32

WB

33

P124 42 6.83 119 55.26 4489.3 979918.13 -29.11 0.01 1.33 -182.24 -172.49

WB 24 P124 42 6.83 119 55.18 4489.3 979918.29 -28.95 0.01 1.28 -182.12 -172.37

WB 25 P124 42 6.83 119 55.14 4489.2 979918.41 -28.84 0.01 1.26 -182.03 -172.28

WB 26 P124 42 6.83 119 55.07 4489.0 979918.50 -28.77 0.01 1.23 -181.99 -172.23

WB 27 P124 42 6.83 119 55.02 4489.0 979918.56 -28.71 0.01 1.21 -181.95 -172.19

WB 28 P124 42 6.83 119 54.97 4489.0 979918.56 -28.71 0.01 1.18 -181.97 -172.21

WB 29 P124 42 6.83 119 54.91 4488.9 979918.54 -28.74 0.01 1.16 -182.02 -172.26

WB 30 P124 42 6.83 119 54.84 4489.5 979918.42 -28.80 0.01 1.13 -182.13 -172.37

WB 31 P124 42 6.83 119 54.78 4488.9 979918.44 -28.84 0.01 1.11 -182.18 -172.41

WB 32 P124 42 6.83 119 54.72 4489.3 979918.21 -29.03 0.01 1.09 -182.40 -172.63

WB 33 P124 42 6.83 119 54.67 4488.9 979918.15 -29.13 0.01 1.07 -182.50 -172.74

WB 34 P124 42 6.83 119 54.60 4489.0 979918.02 -29.25 0.01 1.04 -182.65 -172.89

WB 35 P124 42 6.83 119 54.53 4489.0 979917.86 -29.41 0.01 1.02 -182.83 -173.07

WB 36 P124 42 6.83 119 54.47 4489.9 979917.76 -29.42 0.01 1.00 -182.89 -173.12

WB 37 P123 42 6.83 119 54.41 4489.9 979917.55 -29.63 0.01 0.99 -183.12 -173.35

WB 38 P124 42 6.82 119 54.33 4490.0 979917.51 -29.65 0.01 0.97 -183.16 -173.39

WB 39 P124 42 6.81 119 54.27 4490.5 979917.40 -29.70 0.01 0.95 -183.25 -173.47

WB 40 P124 42 6.82 119 54.19 4490.4 979917.29 -29.83 0.01 0.93 -183.39 -173.61

WB 41 P124 42 6.82 119 54.12 4490.8 979917.14 -29.94 0.01 0.92 -183.53 -173.75

WB 42 P124 42 6.82 119 54.06 4489.8 979917.14 -30.04 0.01 0.91 -183.61 -173.83

WB 43 P124 42 6.79 119 54.00 4489.2 979917.13 -30.06 0.01 0.89 -183.62 -173.84

WB 44 P124 42 6.76 119 53.96 4489.9 979916.99 -30.09 0.01 0.88 -183.68 -173.91

WB 45 P124 42 6.73 119 53.90 4490.1 979916.95 -30.06 0.01 0.87 -183.68 -173.89

WB 46 P124 42 6.69 119 53.85 4489.0 979916.92 -30.14 0.01 0.86 -183.23 -173.95

WB 47 P124 42 6.66 119 53.80 4489.0 979916.89 -30.12 0.01 0.85 -183.72 -173.94

WB 48 P124 42 6.63 119 53.75 4489.2 979916.91 -30.04 0.01 0.84 -183.65 -173.87

WB 49 P124 42 6.59 119 53.69 4489.8 979916.87 -29.96 0.01 0.83 -183.60 -173.82

WB 50 P124 42 6.56 119 53.66 4489.9 979916.90 -29.88 0.01 0.82 -183.53 -173.75

WB 51 P124 42 6.53 119 53.61 4489.8 979916.91 -29.83 0.01 0.82 -183.49 -173.70

WB 52 P124 42 6.51 119 53.57 4489.7 979916.84 -29.88 0.01 0.81 -183.54 -173.75

WB 53 P124 42 6.48 119 53.52 4488.9 979916.77 -29.98 0.01 0.81 -183.61 -173.83

WB 54 P124 42 6.46 119 53.47 4488.5 979916.74 -30.02 0.01 0.80 -183.64 -173.86

WB 55 P124 42 6.43 119 53.43 4489.5 979916.64 -29.98 0.01 0.80 -183.64 -173.86

WB 56 P123 42 6.40 119 53.37 4488.0 979916.59 -30.13 0.01 0.80 -183.75 -173.97

WC 2 P124 42 18.71 119 52.68 4481.6 979951.39 -14.36 0.38 3.99 -164.56 -155.00

WC 3 P124 42 18.71 119 52.72 4487.1 979950.92 -14.31 0.54 4.24 -164.45 -154.90

WC 4 P124 42 18.71 119 52.62 4479.2 979951.73 -14.24 0.24 3.69 -164.66 -155.08

WC 5 P124 42 18.71 119 52.58 4478.5 979951.86 -14.18 0.18 3.53 -164.74 -155.15

WC 6 P124 42 18.71 119 52.55 4478.0 979951.98 -14.11 0.13 3.41 -164.77 -155.18

WC 7 P124 42 18.71 119 52.49 4477.1 979952.16 -14.01 0.09 3.24 -164.81 -155.21

WC 8 P124 42 18.71 119 52.44 4476.9 979952.17 -14.02 0.04 3.08 -164.97 -155.36

WC 9 P124 42 18.71 119 52.38 4476.4 979952.12 -14.12 0.02 2.94 -165.20 -155.58

WC 10 P124 42 18.71 119 52.32 4476.6 979952.02 -14.20 0.01 2.81 -165.41 -155.78

WC 11 P124 42 18.71 119 52.27 4476.9 979952.18 -14.01 0.01 2.72 -165.32 -155.69

WC 12 P124 42 18.71 119 52.22 4477.4 979952.21 -13.93 0.01 2.64 -165.34 -155.70

WC 13 P124 42 18.71 119 52.17 4476.2 979952.26 -14.00 0.01 2.57 -165.44 -155.80

WC 14 P124 42 18.71 119 52.12 4478.6 979952.07 -13.96 0.01 2.49 -165.56 -155.91

WC 15 P124 42 18.71 119 52.07 4478.0 979952.09 -14.00 0.01 2.43 -165.64 -155.98

WC 16 P124 42 18.71 119 52.02 4477.6 979952.13 -13.99 0.01 2.38 -165.67 -156.01

WC 17 P124 42 18.71 119 51.97 4477.8 979952.06 -14.04 0.01 2.33 -165.78 -156.12

11
TABLE 1--CONTINUED

STATION CODE LATITUDE LONGITUDE ELEVATION

DEG MIN DEG MIN FEET

OBSERVED

GRAVITY

MGAL

FREE AIR

ANOMALY

MGAL

TERRAIN

HAND TOTAL

MGAL

BOUGUER ANOMALY

2.67 2.50

MGAL

WC 18 P124 42 18.71 119 51.91 4476.9 979952.11 -14.08 0.01 2.27 -165.84 -156.18

WC 19 P124 42 18.71 119 51.85 4476.7 979952.15 -14.06 0.01 2.22 -165.86 -156.20

WC 20 P124 42 18.71 119 51.79 4477.2 979951.95 -14.21 0.01 2.17 -166.08 -156.41

WC 21 P124 42 18.71 119 51.73 4477.3 979951.81 -14.34 0.01 2.13 -166.26 -156.59

WC 22 P124 42 18.71 119 51.69 4477.5 979951.62 -14.51 0.01 2.10 -166.46 -156.79

WC 23 P124 42 18.71 119 51.64 4477.8 979951.14 -14.96 0.01 2.07 -166.95 -157.27

12
Table 2. Location description code (digit one).

[The number after the alphabetical code indicates the total number

of gravity stations for which the code was used.]

B 45 On level-line benchmark incorporated into U.S. Geological Survey

vertical control system.

N 14 Near benchmark.

P 188 Location of surveyed elevation.

X 5 Near location markers such as section corners.

D 1 Near assumed location of any of the above markers that were

destroyed or not found.

R 1 Lake or reservoir elevation determined from leveling to benchmark.

F 32 Near a location with or without a marker at which a surveyed

elevation is indicated on a published topographic map.

G 58 Near a location (on a manuscript map or a published map) at which

spot elevations are determined by photogrammetry or near a doubtful

F-location.

W 12 Near edge of lake or canal; interpolated elevation or elevation

given for water at unknown height relative to present level.

Table 3. Accuracy of elevations (digit two).

[The number after the numerical code indicates the total number of

stations for which the code was used. Note that uncertainty of

horizontal location tends to reduce the elevation accuracy].

Code Number Accuracy

(feet)

Examples

1 230 0.1 On benchmark; surveyed elevation

2 10 0.5 Elevation difference hand-leveled to nearby

benchmark

3 7 1 Near benchmark or checked water level

4 2 2 Near assumed location of benchmark that was not

found

5 70 5 Near location with 10-foot contour interval

6 36 10 Photogrammetric elevation on map with 20-foot

contour interval

7 1 20 Uncertain location of spot elevation point

13
Table 4. Accuracy of horizontal location (digit three).

[The number after the numerical code indicates the total number of

stations for which the code was used.]

Code Number Accuracy

(feet)

Examples

2 252 84 Near section corners and benchmarks; surveyed

locations

3 80 210 Near road intersection, stream crossings,

hillcrests

4 22 420 Road curve; uncertain spot elevation location

5 2 840 Location depends on odometer measurement or

other estimate

Table 5. Accuracy of observed gravity (digit four).

[The number after the numerical code indicates the total number of

stations for which the code was used. Accuracies are relative to the

value at the Adel base station.]

Code Number Accuracy

(mgal)

Examples

2 3 0.02 Reading repeated several times

3 8 0.05 Repeated reading

4 345 0.10 Non-repeated reading

14
AREA 

Q OF THIS REPORT 

Fimre I. Location of gravity stations and traverses. 
HI' 

4 

SYMBOLS USED 

+ 

Reading by Plouff 

% 

Reading by Conradi 

#---- 

,' --- 

Interpolated value of drift 

at Adel base station 

rt17a 

Reading at Menlo Park, Ca. 

AÃˆ, 

Reading at Alturas, Ca. 

K 

Reading at Klamath Falls, Ore. 

Â 

Reading at auxiliary station 

Figure 2. Gravity drift curve relative to Adel base station.