TESTING GEOPHYSICAL METHODS FOR EXPLORATION OF ECONOMIC ROCK SOURCES IN TIMBER SALE SITES IN WESTERN...
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TESTING GEOPHYSICAL METHODS FOR EXPLORATION OF ECONOMIC ROCK SOURCES IN TIMBER SALE SITES IN WESTERN WASHINGTON, PACIFIC NORTHWEST OF THE UNITED STATES
TESTING GEOPHYSICAL METHODS FOR EXPLORATION OF ECONOMIC ROCK
SOURCES IN TIMBER SALE SITES IN WESTERN WASHINGTON, PACIFIC
NORTHWEST OF THE UNITED STATES CAKIR, Recep (1) ; JENKINS, John E.
(2) ; HAYASHI, Koichi (3) ; SCHILTER, Joseph (1) ; GUFLER, Terran
(1) ; GOETZ, Venice (2) ; BENSON, Matt (4) ; CUMMINGS, Laura (2) ;
SHAFER, Ana (2) ; WALSH, Timothy J. (1) ; HANELL, Casey (2) ; and
NEWMAN, Patricia (5) (1) Geology and Earth Resources, Washington
State Department of Natural Resources, Olympia, WA, USA, (2) Forest
Resources Division, Washington State Department of Natural
Resources, Olympia, WA, USA (3) Geometrics Inc, San Jose, CA, USA,
(4) Northwest Geophysics LLC, Redmond, WA, USA, (5) GSI Water
Solution Inc, Kennewick, WA, USA Line PSTA_015: GPR profile
obtained with 400MHz antenna. Solid line shows possible layer
boundary between overburden (topsoil, soft dig-able rock), and
harder but still rippable rock. GPR profile data were collected on
a line parallel to active seismic line 1000. Line PSTA_016: GPR
profile obtained with 100MHz antenna. The 100MHz antenna allows for
deeper ground penetration at a loss of high detail. GPR profile
data were collected on a line parallel to active seismic line 1000.
Line A: Electric Resistivity model Three million acres of
federally-endowed trust lands in Washington State are managed by
the Washington State Department of Natural Resources (WADNR) State
Lands Division to provide revenue for the construction of public
schools, colleges and other state buildings as well as support for
certain state services. Road rock sources are needed for timber
harvest and can be challenging to locate in rugged terrain
conditions of heavily forested areas. If the desired quality rock
is not found close to a timber harvest area, then the timber sale
project can fail and represent a revenue loss to the trust
beneficiaries. For this reason we tested geophysical methods for
exploration of desired rock in the timber sale areas. The methods
selected are reliable, relatively inexpensive, unobtrusive,
ecologically sound, and portable for use in remote locations. The
primary objectives of our work are to provide a cost effective and
practical geophysical method or combination of methods to 1) locate
new bedrock sources, and 2) expand existing quarries to obtain
quality aggregate required for road construction. In addition, it
is desired to a) identify the extent and thickness of overburden
soils, b) characterize the rock quality beneath the overburden, and
c) identify if groundwater is present and a significant concern.
Our approach includes geologic reconnaissance in combination with
one or more of the following geophysical methods: active/passive
shallow seismic, single-station passive seismic, electric
resistivity (OHM-Mapper), Ground Penetration Radar (GPR), and
Electromagnetic Induction (EMI). Our main goal is to evaluate the
use of various geophysical methods to identify feasible rock
sources. To meet this goal, we tested the geophysical methods at
three sites in western Washington. Results highlight the
feasibility of each geophysical method used for rock exploration in
planned timber harvest areas. Based on our experimental study we
recommend P-wave seismic refraction and GPR surveys for the rapid
exploration of the optimum source rock, and electromagnetic
induction and/or electric resistivity survey methods (supplementary
to seismic and GPR surveys) to explore the ground water and/or
subsurface fracture conditions. Ground Penetrating Radar (GPR)
Active/Passive Multi-channel Shallow Seismic Single-station Passive
Seismic (Tromino) Electromagnetic Induction (EMI) Electric
Resistivity (OHM-Mapper) Multi-channel Analysis of Surface Waves
(MASW) field survey setup and surface- wave data processing steps
Survey Methods Abstract Conclusions References Eastern
PanhandlePerry CreekTiger Mountain (BB- Pit) Survey Locations
Figure 2: Mineable basalt rock classification based on seismic
velocities. The higher the velocity the denser/harder the rock.
Figure 1: Rippability chart displaying the correlation between
seismic compressional-wave velocities, lithological types, and
rippability classification (Caterpillar Inc., 2010). Line 1000:
Active seismic P-wave velocity profile. Comparing the DNR P-wave
velocity to Caterpillar (2010) chart*, dashed lines delineate
hypothetical boundaries between: III Dig-able: 0-800m/s II
Rippable: 800-1800 m/s* II or I Rippable/non-rippable
intermediate/marginal zone: 1800-2400 m/s* I Non-rippable: >2400
m/s* Cakir, R. and Walsh, T.J. (2011) Shallow seismic site
characterizations at 23 strong-motion station sites in and near
Washington State. U.S. Geological Survey Award No. G10AP00027.
[http://earthquake.usgs.gov/research/external/reports/G10AP00027.pdf]
Caterpillar Inc., 2010, Caterpillar performance handbook (40 th
ed):Caterpillar, Inc., Peoria, III., 1, 442 p. Geometrics Inc.
(2009a) SeisImager/SW software manualWindows software for analysis
of surface waves: Geometrics Inc., version 3.3, 314pp.
[http://www.geometrics.com] Geometrics Inc. (2009b) SeisImager/2D
software manual; version 3.3, 257pp. [http://www.geometrics.com]
Powers, M.H., and Burton, B.L., 2012, Measurement of near-surface
seismic compressional wave velocities using refraction tomography
at a proposed construction site on the Presidio of Monterey,
California; U.S. Geological Survey Open-File Report 2012-1191, 17
p. Tzanis, A., 2010. matGPR Release 2: A freeware MATLAB package
for the analysis & interpretation of common and single offset
GPR data, FastTimes, 15 (1), 17 43. Waypoint 795: Single station
passive seismic data taken with a Tromino unit. The Tromino results
show estimated P-wave velocities (Vp) of: 539m/s @1.0m 1158m/s
@3.9m These results correlate with velocities seen at similar
depths on active seismic line 2000. Line F_189: GPR profile with
270MHz antenna. Solid line shows possible layer boundary between
overburden (topsoil, soft dig-able rock), and harder, but still
rippable rock. GPR data were collected on a line parallel to active
seismic line 1000. Line 3000: Active seismic P-wave velocity
profile. Comparing the DNR P-wave velocity to Caterpillar (2010)
chart*, dashed lines delineate hypothetical boundaries between: III
Dig-able: 0-800m/s II Rippable: 800-1800 m/s* Line F_190: GPR
profile with 270MHz antenna. Solid line shows possible layer
boundary between overburden (topsoil, soft dig-able rock,), and
harder, but still rippable rock. GPR data were collected on a line
parallel to active seismic line 3000. Line 2000: Active seismic
P-wave velocity profile. Comparing the DNR P-wave velocity to
Caterpillar (2010) chart*, dashed lines delineate hypothetical
boundaries between: III Dig-able: 0-800m/s II Rippable: 800-1800
m/s* II or I Rippable/non-rippable intermediate/marginal zone:
1800-2400 m/s* Waypoints 785-784: GPR profile obtained with 270MHz
antenna. Solid line shows possible layer boundary between
overburden (topsoil, soft dig-able rock), and harder but still
rippable rock. GPR profile data were collected on a line parallel
to active seismic line 2000. Line 3001: Active seismic P-wave
velocity profile. Comparing the DNR P-wave velocity to Caterpillar
(2010) chart*, dashed lines delineate hypothetical boundaries
between: III Dig-able: 0-800m/s II Rippable: 800-1800 m/s* II or I
Rippable/non-rippable intermediate/marginal zone: 1800-2400 m/s*
Waypoints 778-779: GPR Profile obtained with 270MHz antenna. Solid
line shows possible layer boundary between overburden (topsoil,
soft dig-able rock), and harder, but still rippable rock. GPR
profile data were taken on a line parallel to active seismic line
3001. Line 1000: Active seismic P-wave velocity profile. Comparing
the DNR P-wave velocity to Caterpillar (2010) chart*, dashed lines
delineate hypothetical boundaries between: Electric Resistivity
Results III II III II III II III A A A A AA III Dig-able: 0-800m/s
II Rippable: 800-1800 m/s* II or I Rippable/non-rippable
intermediate/marginal* zone: 1800-2400 m/s I Non-rippable: >2400
m/s* B B B B B B B- B A- A A- A A A A A A A B B B B B- B B B
Electromagnetic Induction (EMI) Survey using the Geonics EM31-MK2
Fast Mapping of Conductivity - 5x5m grids established to
accommodate the 3.7meter length of the coil spread. A A A A B B B B
B B 1)Geophysical methods can be used to identify the location of
mineable rock for road aggregate. 2)Study area source rocks include
basalt, basalt breccia, and intrusive basalt. 3)Our rock quality
criteria can be compared with the Caterpillar (2010) results that
may be correlated to seismic P-wave velocity to mining method
(rippable vs. non-rippable). 4)Recommendations for Geophysical
Survey Methods: a.Best: Active-source seismic P-wave refraction
method yields the most detail in the fastest timeframe for shallow
depths up to 10m where it is needed for surface mining b.Second
best: Ground Penetrating Radar (GPR) is the preferred method for
ease of use but surface conditions must be optimum to run the
survey c.Good: Electric Resistivity(ER) and/or Electromagnetic
Induction (EMI) indicates the presence of water which suggests deep
weathering or abundant fractures. Advantages: rapid implementation;
optimum conditions not necessary d.Poor: Single-Station Passive
Seismic (SSPS) does not show details near surface; affords a look
at deep structure or soil/rock interface between 100-200m. This is
not an optimum method for rock exploration which needs shallow data
up to 10m. However, this method may be used for a preliminary rapid
survey to understand the rough shear-wave velocity distribution in
the area. This method is not reliable if there are high horizontal
variations of soil/rock or weathered rock layers. For example, at
the Tiger Mountain BB-Pit area we found that the SSPS values
correlated well with Vp values in Line 2000. 5)More studies are
needed in other rock types to relate geology (hardness, density,
and porosity) to geophysical parameters (P- and S-wave velocities,
resistivity/conductivity) for future quantitative analyses. High
Speed Capacitively-Coupled Resistivity System (www.Geometrics.com)
OHM-Mapper Survey