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8th EEGS Symposium on the Application of Geophysics to Engineering and Environmental Problems
- Conference date: 23 Apr 1995 - 26 Apr 1995
- Location: Orlando, Florida, Canada
- Published: 23 April 1995
81 - 100 of 104 results
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Em Mapping Of Pollution Plumes
Authors S.K. Verma and S.P. SharmaOne of the major contemporary applications of the controlled source EM methods involves
mapping of subsurface pollution plumes. Generally such plumes occur in the form of
thin layers that make good resistive or conductive targets depending on electrical characteristics
of the plume and the polluted zone. The problem of mapping pollution plumes is thus
well-suited for the application of the electrical or electromagnetic (EM) methods. Since such
problems are mostly encountered in industrial and/or populated areas, with limited space
available for surveys, the inductive EM methods are found to be particularly useful.
A comparative study of the performance of various dipole EM systems in the mapping of
pollution plumes in different, geoelectrical scenarios is made. A small section is also devoted
to the comparison of resolutions obtained by employing dipolar and large loop transmitters
considering joint-inversion with D.C. (Schulumberger) data. Singular value decomposition
analyses are performed to arrive at the quantitative estimates of the resolution of the target
plume obtained by various ERI systems.
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Derivation Of Conventional Geotechnical Parameters From Nuclear Borehole Logging
Authors Olli Okko and Jouko TörnqvistThe radiometric method of measuring density and moisture in-situ with the Russian made probes PPGR and
VPGR is calibrated for logging in cased holes. The accuracy of the radiometric gamma-gamma and neutronneutron
logging methods depends on the material properties and on the time allowed for the integration of the
back-scattered radiation energy, This paper presents case studies describing the accuracy and repeatability of the
measurements in monitoring of changes in water content and in density of soils and soil structures.
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Siting Of A New Landfill For Solid Wastes In Tece Kingdom Of Saudi Arabia
Authors T.A. Mokhtar, M.H. Basyoni and H.S. SadekSiting investigations were conducted to locate solid waste disposal landfill sites for an urban district of
600,000 inhabitants in an arid province to the west of the Kingdom of Saudi Arabia. This paper presents the
systematic approach followed during the process of site selection as well as the preliminary studies achieved in the
first selected landfill site (Ma&an-l). This site represents a natural closure covered by alluvial deposits and
surrounded by a series of low to moderate relief hills from all sides. It has a small narrow outlet that drains towards
the main valley at the down stream part relative to the district. The surrounding hills are exposures of the
Precambrian basement rocks of mainly quartz diorite. The closure of the site is about 1.5 km long and 600 m wide.
The site was subjected to geological, hydrological, and ground geophysical studies that were primarily executed to
obtain the necessary information for subsequent engineering studies. These studies revealed that the location
satisfies most of the landfill siting considerations such as geologic and hydrologic conditions, surface water
hydrology, accessibility, location restrictions, available capacity, and other local topographic and environmental
conditions. In addition, the site acquires numerous natural geological barriers that can be effectively employed in
the engineering implementations. The paper provides an example for site selection of solid waste landfills in arid
regions.
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A Finite Element Model Of Moisture Flow And Distribution Within A Sanitary Landfill
More LessLeachate generation at municipal solid waste facilities has become an increasing public concern, especially
in light of numerous documented groundwater and surface water contamination incidents which were directly attributable
to nearby landtill sites. Unfortunately, our understanding of the processes involved in the production of contaminated
leachate is limited. Landfill excavation studies have indicated a strong correlation exists between refuse
moisture content and the amount of degraded refuse, suggesting the amount and distribution of moisture within the
landfill are key determinants of leachate formation. Current models of landfill systems are used to estimate total
leachate production, however they are limited in their ability to characterize the patterns of moisture distribution
within the landfill, partly due to the assumption of homogeneous landfill material properties. Accordingly, a two
dimensional finite element computer model, which incorporates the hydraulic properties of various land811 materials,
has been developed to examine the effects of anisotropic conditions on moisture distribution patterns within a landfill.
The model is based on mathematical expressions of unsaturated flow in porous media. The landtill physical properties
input to the model were obtained from test landfill cells constructed and operated by the Delaware Solid Waste
Authority (DSWA). The model predicted unique moisture distribution patterns, consistent with the given antecedent
rainfall amounts, however it consistently underestimated peak leachate generation measurements. While further
investigation is warranted, these results highlight the importance of including various landfill material properties, i.e.,
hydraulic conductivities, when modeling the moisture flow and distribution within a landtill system.
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Physical Processes Associated With Environmental Impacts Due To Mining Exploitation
More LessMany years of intensive mining exploitation in Poland have caused very serious environmental disturbances in
mining reas. They include:
- discharge of untreated saline waters around tailings dumps and waste ponds,
- development of cavities from uneven subsidence of topset rocks, resulting in settling or collapse of buildings,
roads and other elements of building infrastructure,
- seismic tremors and abrupt releases of energy, which pose hazards to miners and surface structures.
A special three-year research program to locate environmental changes in Polish mining areas employed
different geophysical methods to assess different kinds of problems. Two processes seem particularly important
in environmental disturbances that result from mining activities. One is the develpoment of a fracture zone
around an excavated area, and its changes in time. The second is the flow of liquids and gasses through a
cracked and porous medium, and resulting changes in its physical properties.
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Deep Tunnel Detection Using Crosshole Radar Tomography
Authors Ken Hauser, Michael Jackson, John Lane and Richard HodgesAs part of continuing research aimed at the detection of subsurface tunnels and voids, the U.S. Bureau of Mines
recently completed a cooperative study with the U.S. Geological Survey at a surface gold mine in the Black
Hills mining district of South Dakota. The occurrence of older, poorly mapped mine workings in the section
create a consistent health and safety concern for mine employees as well as economic concerns about potential
damage to equipment during daily operations at the mine. Accurate knowledge regarding the location of these
abandoned tunnels prior to interception by the current mining operation would be beneficial. Previous research
efforts on site have demonstrated the suitability of several surface geophysical technologies in detecting shallow
workings which present an immediate problem in the safe conduct of the mine operation. Another concern is
the existence of deeper abandoned mine tunnels, which occur further in advance of the surface mining operation.
In the design and development of a new mine pit, the placement of access roads over a tunnel would be
hazardous, due to the volume of traffic and the weight these haulage trucks can carry. In this study we evaluate
cross borehole radar tomography methods which might be used to image mine openings in the deep subsurface,
and lead to more prudent placement of pit haulage roadways. A pulsed radar system was used to collect both
velocity and amplitude information about local rock conditions, and multiple borehole data allowed for the use
of 3-D imaging techniques.
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Airborne Radiometric Mapping Of The Environmental Impact Of Gold And Uranium Mining In Gauteng Province, South Africa
By Henk CoetzeeGold Mining began in the Witwatersrand Basin (see Fig. 1) in 1886. Since then, the goldfield has grown into the world’s
major producer of gold. The region has also been a major uranium producer, gold and uranium coexisting in the
conglomerate ores.
The gold and uranium accumulated together in Archaean times, with a non-oxidising atmosphere, and have been
preserved relatively intact in the Witwatersrand Supergroup orebodies. Uranium is, however, highly soluble under
oxidising conditions and will be mobilised to any system exposed to a present day atmosphere. Uranium in mine tailings
dams will therefore move rapidly into ground- and surface water systems, polluting these resources.
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Spontaneous Potential Surveys Around Pumping Wells
By John JansenSpontaneous potential (SP) surveys have been used for several decades for seepage studies on dam sites. The method is particularly attractive because it is fast, inexpensive, and has
been shown to be very effective at mapping seepage paths. Bogoslovsky and Ogilvy (1972) reported using SP measurements as a substitute for monitoring wells around pumping wells. While this suggestion is probably extreme, it does point to several useful applications for water supply, dewatering, and ground water remediation projects. Many aquifers are inhomogeneous or
anisotropic. Often, permeability variations are small scale and difficult to define with traditional test drilling methods. Measuring SP anomalies around pumping wells has the potential to
map pathways of maximum ground water flow and select strategic monitoring well locations Because very little could be found in the way of follow up investigations to the work of Bogoslovsky and Ogilvy, the author has been acquiring SP data around pumping wells as time and site conditions allowed. This poster presents the results from several SP surveys around pumping wells, conducted as part of larger projects. None of the surveys were designed specifically to test the SP method. Controlled experiments are still needed to confirm these preliminary results and explore the limits of the application of this method. The intent of this paper is revive Bogoslovsky and Ogilvy's idea and stimulate additional investigation to explore the potential of this approach.
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Revisiting A 1955 Resistivity Survey Over A Buried Bedrock Valley Aquifer
More LessElectrical earth resistivity surveying has been a part of the groundwater resources program at the Illinois State
Geological Survey (ISGS) since 1932. In a project conducted in 1994, we used a computer-controlled resistivity
system to collect vertical electrical soundings (VES) over the same area covered by a resistivity profiling survey
done in 1955. Similarities between the two surveys provide an opportunity to evaluate changes made in the resistivity
method over the past 40 years.
Both surveys:
. used the Wenner electrode configuration with similar maximum electrode separations and collected
data on a grid pattern with approximately ?&mile station spacings;
. were part of studies assessing the groundwater potential of the Ticona Buried Bedrock Valley aquifer
as a municipal water supply for the town of Streator in central Illinois;
. clearly delineated the boundaries of the aquifer; and
. helped demonstrate that the aquifer is not adequate to meet the water needs of Streator.
The Ticona Bedrock Valley (fig. 1; Willman, 1940) was a Quaternary drainageway ancestral to the modern
Illinois River Valley. The Ticona river was probably active during the Illinoian glacial age (about 300,000 to
100,000 years ago) when it eroded a valley into Pennsylvanian shale, sandstone, and limestone and possibly into the
underlying Ordovician dolomite. Upon the advance of the Woodfordian glaciers about 25,000 years ago, the old
valley was completely filled, and the drainage was diverted to a new valley 6 miles to the north. In the old valley,
coarse grained glacial outwash and older alluvium now constitute a sand and gravel aquifer 50 to 80 ft thick. The
top of the aquifer is about 530 to 550 ft above mean sea level (Randall, 1955). The aquifer is buried beneath 75 to
100 ft of younger glacial till, outwash, and lacustrine sediments.
The village of Grand Ridge (population 680) draws its water from the aquifer, as do several dozen landowners
in this rural area of central Illinois. Currently, about 0.75 million gallons per day (mgd) is withdrawn from the aquifer.
The city of Streator (population 14,800) 6 miles south of the buried bedrock valley, has twice evaluated the
Ticona Bedrock Valley aquifer as a water source. In 1954-56, Northern Illinois Water Corporation (NIWC), which
supplies water to Streator, considered replacing its 6 to 8 mgd surface water supply with groundwater. Presently,
NIWC is reviewing several options to control seasonally fluctuating nitrate levels in the surface water supply. One
option is blending up to 3 mgd of groundwater with the surface water to adjust the nitrate concentrations. The applicability
of the 1955 and 1994 surveys to NIWC was limited by the high cost of transporting the water from the well
head to production facilities in Streator.
The Ticona Bedrock Valley aquifer is an ideal subject for resistivity surveys because the thick sand and gravel
that make up the aquifer contrast sharply in resistivity with the overlying glacial till and underlying shale.
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The Application Of Reflection Seismology And Hydrogeology In An Interdisciplinary Approach To Sole-Source Aquifer Management Planning: Subsurface Investigation Of Missoula Flood Deposits That Form The Sole Source Aquifer For Spokane, Washington
Authors Michael King, Stephen P. Palmer, Charles R. Gruenenfelder, Stan Miller and Lars HendronThe Spokane Aquifer is part of a regional groundwater system called the Spokane Valley -Rathdrum Prairie Aquifer which
encompasses portions of the north Idaho panhandle and eastern Washington near Spokane. The Spokane Aquifer is
developed within major buried valleys which constitute the present day and ancestral valleys of the Spokane River. The
aquifer is known to be one of the most transmissive alluvial-type aquifers in the United States, and is the major source of
drinking water for over 350,000 people living in the Spokane Valley area. This designated sole-source aquifer consists
predominantly of sand-to-boulder sized sediments deposited by catastrophic outburst floods from episodic draining of
Pleistocene glacial Lake Missoula. The unconsolidated deposits consists of coarse-grained main channel sediments in the
Spokane Valley, and tiner-grained eddy deposits in tributary valleys. The deposits overlie relatively impermeable, and lowyielding
Precambrian to Cretaceous age crystalline bedrock, Miocene clay deposits, and Columbia River basalts. The flood
deposits typically are 400 to 600 feet thick in the main valley. The aquifer is unconfined throughout most of the valley, and
typically exhibits a strong degree of hydraulic interconnection with the Spokane River, Previous water balance estimates
for the Spokane Aquifer have relied upon little direct data on aquifer thickness. Knowledge of the aquifer’s thickness and
areal distribution is vitally important for comprehensive aquifer management and wellhead protection delineation.
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Joint Orientations And Near-Surface Structure And Stratigraphy In The Vicinity Of Large Sediment Boils Erupted During A Major Earthquake
Authors R.D. Bolger, J.R. Pelton, L.M. Liberty and C.J. WaagSediment boils formed during the 1983 Borah Peak (Idaho) earthquake in the vicinity of Chilly Buttes occur in a NNW-trending zone parallel to the orientation of NNW-trending and approximately vertical joints mapped in nearby exposures of the limestone bedrock. Seismic reflection profiles (unmigrated) indicate that the upper surface of the limestone slopes to the northeast (away from Chilly Buttes) at approximately 14’, and that the overlying alluvium is relatively thin (< 85 m) beneath the 1983 sediment boil zone. These results are consistent with the prevailing hypothesis that water erupted to form the 1983 Chilly Buttes boils was derived from tectonic disturbance of the limestone aquifer, and suggest that the NNW joints and the relatively
thin alluvial overburden are factors that helped localize the boil zone near Chilly Buttes. Trenching of a moderatelysized boil (5-m diameter) shows downward bending of a shallow (< 1.5-m depth) caliche layer beneath the vent, consistent with the downward warping of the reflection pattern in a radar profile acquired before trenching the boil. Similar patterns in other radar sections suggest that buried boils (no surface expression), perhaps related to prehistoric earthquakes, exist in the shallow subsurface within the range (< 3 m) of backhoe excavation.
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Blue Hole And Beachrock Geophysics
Authors Paul J. Wolfe, Cindy Carney and Mark R. BoardmanGeophysical investigations provided valuable information on the geology and water resources of two islands
in the Bahamas. A group of faculty and students from Wright State University and Miami University have
conducted several geophysical surveys in support of larger research projects. Three techniques (resistivity, ground
penetrating radar, and seismic refraction) proved to be useful.
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Pulled Array Continuous Electrical Sounding Pa - Cves
Authors K.I. Sørensen and K.M. SørensenThe electrical profiling method is a powerful technique for mapping the near
surface geology. The increasing need for detailed and fast investigations of the protective
clay caps of the aquifers has renewed the focus on the method. In this context the
PA-CEP method was developed. The method applies an electrode array mounted on a tail,
and measurements are carried out continuously while actively pulling the electrodes. The
PA-CEP method has enabled fast and reliable profiling of large areas providing
surprisingly good insight into the stratification of the survey areas. However, the method
is a profiling technique with only few electrode arrays and therefore allows only limited
quantitative interpretation.
A new method, Pulled Array Continuous Vertical Electrical Sounding, PA-CVES,
is under development. Using this technique measurements are performed simultaneously
and continuously in several arrays. Hence the PA-CVES method provides vertical
resistivity soundings closely spaced along a profile line.
The measurements are interpreted with 1D smoothness constrained resistivity
models with many layers and fixed layer boundaries, and in the intervals where laterally
strongly varying data sets are encountered 2D interpretation techniques are applied.
The PA-CVES method as a continuous and fast method will have a great potential
in groundwater investigations, in prospecting for rawmaterials and in geotechnical
investigations, because it provides detailed and reliable geological interpretations in a
manner not obtained by traditional techniques.
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Pulled Array Transient Electromagnetic Method Pa - Tem
Authors K.I. Sørensen, F. Effersø and A.J. ChristensenSteadily growing abstraction of ground water together with the impact of pollution
from surface infiltration have increased the need for hydrogeological investigations of
aquifers. The mapping of subsurface resistivity structures using electrical and
electromagnetic methods has gained a central role in the set-up of hydrogeological
models of catchments in Denmark.
In this context the transient electromagnetic method (TEM) has proven to be a
powerful tool. Regional investigations with TEM have produced results, which leave no
doubt as to the ability of the method to delineate fresh-water sandy aquifers in more well
conducting surroundings of clay or salt water. These results have been obtained using a
dense grid of measurements and demonstrate the necessity to estimate the data quality by
correlating nearby data sets. The fact that these investigations are often carried out in
densely populated areas, where the cultural noise level is high, accentuates this even more.
Investigations meeting these demands require much field work thus increasing the cost of
the survey.
A new technique, Pulled Array Transient Electromagnetic Method (PA-TEM), is
under development. With this method a transmitter coil and a receiver coil are towed
across the surface along profile lines while measuring. With this technique the cost of the
field work is drastically reduced. Furthermore, as the measurements are recorded very
densely, nearby data sets can be correlated to ensure good data quality, and distortion
from cultural effect from hidden powerlines, fences, etc. in the data sets is more easily
discovered and reduced.
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3D Gpr Imaging Of A Sand-Gravel/Clay Boundary At Hill Air Force Base, Utah
Authors Roger A. Young and Jingsheng Sun3D Ground Penetrating Radar survey (GPR) defines the boundary between a sand/gravel unit and an
underlying clay aquitard at Hill Air Force Base, Utah, Despite attenuation due to an artificial clay cap
approximately 2 ft thick, a strong reflection from a depth of 20-30 ft occurs. Lateral and vertical resolution along
the boundary are approximately 2 ft and 1 ft, respectively. There is abrupt topographic variation of 5 ft over
distances of 20 ft or less in the surface of the clay layer. This variation may have a major influence on ground
water movement and on the local accumulation of chlorinated organic pollutants.
This study shows that a three-dimensional GPR image provides far better definition of geologic
boundaries than does projection of soil boring logs into two-dimensional profiles. In the present case this highresolution
image provides a detailed estimate of target depths for future soil borings and will facilitate the choice
of the location of cells to be used for testing new remediation techniques.
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Ground Penetrating Radar And Electromagnetic Profiling Of Bedrock Topography At The Portsmouth Gaseous Diffusion Plant, Piketon, Ohio
Authors R.D. Kaufmann, W.E. Doll, D.H. Green, M.S. Peterson and B.A. RichardsLow-frequency ground penetrating radar (GPR) and electromagnetic profiling (EM-3 1 and EM-34) surveys were
carried out at the Portsmouth Gaseous Diffusion Plant (PGDP) in Pike County, Ohio. The primary objective of the
surveys was to profile sedimentary bedrock topography beneath unconsolidated fluvial and lacustrine deposits. The
EM surveys show high conductivity (8.5-39 mS/m) values for the unconsolidated sediments and underlying bedrock,
presenting a hostile environment for GPR. The low-frequency GPR, however, penetrated to bedrock depths of up
to 10 m, which exceeds the predictions of forward modelling. The data show that low-frequency GPR is effective
in this lossy-dielectric environment, and is not accurately modelled using typical low-loss assumptions.
The site occupies a buried channel of the late-Tertiary Portsmouth River (Figure 1). The unconsolidated deposits
include the clay-rich Minford formation, which extends from the surface to approximately 4 m, and the gravel and
clay bearing sand of the Gallia formation. The Gallia deposits are part of interbraided fluvial channels which vary
in thickness, and are laterally heterogeneous. It is the bedrock beneath the Gallia that is the primary target of these
surveys. The bedrock is generally the Sunbury Shale or, where the channel is more deeply eroded, the Berea
Sandstone.
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Time Domain Electromagnetic Migration In Inel Rwmc Cold Test Pit Characterization
Authors Michael S. Zhdanov, Peter Traynin, Oleg Portniagune and H. David Mac LeanThe main task of the conducted research was interpretation of time domain
electromagnetic (TDEM) data set acquired at the Cold Test Pit within the
Radioactive Waste Management Complex (RWMC) at the Idaho National
Engineering Laboratory (INEL) using Electromagnetic Migration method.
There were several publications dedicated to the development of simple
and fast inversion technique for the processing of transient electromagnetic
data (Eaton and Hohman, 1989; Macnae and Lamogntagne, 1987;
Barnet, 1984). Majority of these papers have been based on equating the
transient response, measured at the surface of the Earth, to the EM field of
current filament images of the source (Nabighian, 1979).
In this paper we have developed and used a different approach to processing
of transient data, based on downward extrapolation in reverse time.
We call this method the time domain electromagnetic migration
(Zhdanov et al., 1994). The technique has been developed for the transformation
of the transient electromagnetic migration field into resistivity
images of the vertical cross-section. We discuss the principles of electromagnetic
migration and resistivity imaging and present the results of application
of the method for the imaging of TDEM data set from the RWMC.
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Review Of The Comparison Test Of Short Pulse And Synthetic Pulse Ground Penetrating Radars At The Dahlonega Test Site
More LessThis poster session combines two related projects that ENSCO, Inc. has been involved in
during the past year. These projects are concerned with the ability to detect rather large
underground voids or targets at considerable depths in the complex geology.
The two related projects are:
1) The development of the Dahlonega Test Site (DTS) which is located in Northeast
Georgia, and
2) Our side-by-side comparison tests of the short pulse GSSI SIR-10 system with the
ENSCO developed synthetic pulse prototype system.
The synthetic pulse system is based on a stepped frequency concept as contrasted with the
impulse radar type. The rationale is that the synthetic pulse system allows the operator the ability
to “build” a time domain pulse with more effective energy than can be achieved by the conventional
short pulse (impulse) type system.
Other considerations include the increased emphasis on the higher frequencies (by the
potential of increasing the energy of these frequencies) thereby increasing the target resolution, and
avoiding those frequencies which may be detrimental to a nearby communication system, for
example.
As part of this poster session we will illustrate the DTS and its unique features, and then
follow this with our strategy in making our comprehensive comparison of the two ground
penetrating radar systems which we were evaluating.
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Groundwaterflowvelocitymeasurementsinasinkholeatthe Weeig Island Strategic Petroleum Reserve Facility, Louisiana
Authors Sanford Ballard and James GibsonIn 1992, a sinkhole was discovered above a Strategic Petroleum Reserve storage facility at Weeks
Island, Louisiana. The oil is stored in an old salt mine located within a salt dome. In order to assess the
hydrologic significance of the sinkhole, an In Situ Permeable Flow Sensor was deployed within a sandfilled
conduit in the salt dome directly beneath the sinkhole. The flow sensor is a recently developed
instrument which uses a thermal perturbation technique to measure the m.agnitude and direction of the full
3-dimensional groundwater flow velocity vector in saturated, permeable materials. The flow sensor
measured substantial groundwater flow directed vertically downward into the salt dome. The data
obtained with the flow sensor provided critical evidence which was instrumental in assessing the
significance of the sinkhole in terms of the integrity of the oil storage facility.
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Composite Refraction-Reflection Stack Sections: Imaging Shallow Subsurface Features
Authors Cahit Çoruh, William J. Domoracki, John K. Costain, Oguz Selvi and Dale E. StephensonSeismic data sets are gcncrally processed to intcrprct subsurface features using either refracted or reflected
arrivals, but not both. In processing seismic reflection data, refracted arrivals are commonly discarded
and considered to hc noise during the early stages of the processing flow. This paper addresses a
seismic data processing scheme that utilizes both reflected and refracted arrivals simultaneously to image
shallow subsurface geologic features. In addition to conventional reflection stack sections, refraction stack
sections are protluccd using split-spread and/or off-end data after applying a linear-moveout correction that
adjusts the refraction arrival times into modified intercept (delay) times that correspond to the related reflection
times. Velocities necessary for the adjustment arc obtained from constant-velocity display panels
that arc generated on the basis of the linear-movcout correction for the refracted first and later arrivals. It
is shown that the velocity obtainrd from the test panels is the actual velocity of a subhorizontal refractor
in which the critically refracted waves travel. In the case of a dipping refractor, the velocity obtained is an
apparent velocity. ‘I‘he refraction stacks produce cxtrcmcly good refracted signals representing horizons that
can be correlated with corresponding reflections and/or synthetic seismograms from well log data. This
correlation forms the justification for constructing composite refraction-reflection stack sections by combining
the reflection and refraction arrivals in common midpoint gathers. This procedure minimizes loss
of seismic data and yields composite refraction and rcflcction stack sections that recover additional images
of shallow subsurface features.
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