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25th Symposium on the Application of Geophpysics to Engineering & Environmental Problems
- Conference date: 25 Mar 2012 - 29 Mar 2012
- Location: Tucson, USA
- Published: 25 March 2012
81 - 100 of 195 results
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NEAR-SURFACE SEISMIC SURVEYING ALONG THE GREEN VALLEY FAULT, SAN FRANCISCO BAY AREA, CALIFORNIA
Authors Mitchell Craig, Uyanga Ganbaatar and Joanne ChanSeismic reflection surveying was conducted at the Green Valley fault, located in the San Francisco Bay Area, California, with the goal of identifying subsurface stream channels for use in measuring fault offset and slip rate. Three 180-m long, fault-parallel profiles were recorded in 2009 near the site of previous paleoseismologic investigations, including near-surface geophysical surveys. A previous seismic refraction survey identified a trough-shaped, low velocity body on the east side of the fault at depths of 5-12 m, interpreted as a stream channel truncated by the Green Valley fault. The present work was undertaken with the goal of finding the corresponding portion of the channel on the west side of the fault, presumably offset to the north due to motion on the fault during approximately the past 10 ka. Seismic reflection data were recorded in order to obtain higher-resolution and more extensive coverage. The new survey provided excellent resolution of near-surface stratigraphy at depths of 80-375 m, but did not provide sufficient resolution at shallower depths to permit correlation with data from the earlier seismic refraction survey, which had a maximum depth penetration of only about 15 m. The new reflection data appear to image lateral variations in fluvial stratigraphy at depths of approximately 100 m that could be used to measure fault offset in a future study.
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GEOPHYSICAL ANALYSIS OF THE UPPER SIX METERS OF SOIL, EAST-CENTRAL DUGWAY PROVING GROUND, IN SUPPORT OF MILITARY AND HOMELAND SECURITY INTERESTS
Authors Kevin Parkman, Lee Perren, Seth Broadfoot, Jason McKenna and Lillian WakeleyOctober 2010 field investigations in the east-central part of Dugway Proving Ground included geophysical investigations coupled with extensive soil sampling and field investigations of stratigraphy in support of military and homeland security interests.
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DEPTH OF CINDER DEPOSITS AND WATER-STORAGE CAPACITY AT CINDER LAKE COCONINO COUNTY, AZ
Authors Jamie Macy, Lee Amoroso, Jeffrey Kennedy and Joel UnemaThe 2010 Schultz fire northeast of Flagstaff, Arizona burned over 14,000 acres on the east side of the San Francisco Mountain from June 20 to July 3. As a result, several drainages in the burn area are now more susceptible to increased frequency and volume of runoff and downstream areas are more susceptible to flooding. Resultant flooding in areas down-gradient of the burn has resulted in extensive damage to private lands and residences, municipal water lines, and roads. Coconino County, which encompasses Flagstaff, has responded by deepening and expanding a system of roadside channels. These channels move flood water away from communities and into an area of open Forest Service lands, known as Cinder Lake, where rapid infiltration can occur. Water that has been recently channeled into the Cinder Lake area has infiltrated into the volcanic cinders and could eventually migrate to the deep regional groundwater flow system that underlies the area. It is unknown as to how much water can potentially be diverted into Cinder Lake, and Coconino County is interested in determining how much storage is available. The U.S. Geological Survey conducted geophysical surveys and drilled four boreholes to determine the depth of the cinder beds and their capacity for potential water storage. Results from the geophysical surveys and boreholes indicate that the cinders are underlain by basalt at about 30 ft below land surface. Total porosity for the upper 30 ft of cinders was calculated at 43 percent for an area of 300 acres surrounding the boreholes, which yields a total potential subsurface storage for Cinder Lake of 3,900 acre-ft. Ongoing monitoring of storage change in the Cinder Lake area was initiated using a network of gravity stations.
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CREDIBILITY OF THE OPTIMUM XY SPACING OF THE GENERALIZED RECIPROCAL METHOD IN INTERPRETATION OF SHALLOW REFRACTION SEISMIC DATA
By Hamdy SeisaThe shallow seismic refraction technique has inherent problems, such as the undetected layers, ambiguities, first and later arrivals. Other main problems are related to the interpretation techniques themselves. Most of them are restricted to simple models, but the generalization is responsible to false interpretations The Generalized Reciprocal Method (GRM) is suggested to be used for mapping subsurface structures with lateral variations. This method depends mainly on a heuristic single parameter called the optimum XY distance. At the optimum XY separation, the rays to each geophone emerge from near the same point on the refractor. Since the GRM has heuristic assumptions and has no mathematical derivation, more uncertainties are raised in its application, even in case of simple models. The lack of constant XY spacing in all cases (except the horizontal ones) will lead to more uncertainties in its application. The optimum XY value is based on a heuristic determination and it is always a doubtful matter. The uncertainties of the optimum XY spacing will be discussed on two synthetic models.
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LINKING LABORATORY MEASUREMENTS OF GEOPHYSICAL PROPERTIES TO ENGINEERING PROPERTIES, QUANTITATIVE AND QUALITATIVE MINERALOGY, AND FIELD DATA
Authors Ryan North, William Folks, Julie Kelley and Jason McKennaNear-surface geophysics spans a wide range of methodologies and applications but one common theme is the desire to understand the relationships between the properties of the soil and the measurement methods. As part of a multi-year series of projects the U.S. Army Engineer Research and Development Center has been performing field geophysical data collections and soil sampling on multiple scales at a range of locations both domestically and internationally. This presentation will cover the range of measurements that have been performed to fully characterize the geophysical properties (electrical resistivity, magnetic susceptibility, dielectric permittivity, p-wave and s-wave velocities, moisture content measured with lowfield nuclear magnetic resonance), engineering properties (grain size distribution, moisture content, compressive and shear strength), and qualitative and quantitative mineralogy (X-Ray Diffraction, X-Ray Fluorescence, Scanning Electron Microscopy, Differential Thermal Analysis, Differential Scanning Calorimetry, Thermal Gravimetric Analysis). The geophysical properties have been measured over a frequency range from 10 mHz to 8.5 GHz. There will also be a discussion of some of the methodologies that have been employed for analysis and interpretation of individual results and also how to link the physical properties across disciplines. A dataset of this size requires several types of analyses to identify correlations in physical properties and allow more detailed explorations of the relation between physical properties.
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EXPLORING THE POTENTIAL OF NEAR-SURFACE GEOPHYSICAL METHODS TO DELINEATE A SHALLOW HARDPAN IN A SOUTHEASTERN U.S. SANDY COASTAL PLAIN SOIL
Authors Barry Allred, Hamid Farahani and Ahmad KhalilianA hardpan, which is a dense soil layer near the ground surface, is an undesirable feature of many soils in the Southeast U.S., especially sandy Coastal Plain soils. Shallow hardpans restrict root growth and water penetration through the soil profile, in turn reducing the effective crop root zone and thereby limiting crop production. Knowledge of hardpan existence, depth, and spatial extent is valuable, and can be used by farmers to improve soil, water, and crop management. This hardpan problem is similar to challenges faced with claypan soils in the Midwest U.S. (i.e., Missouri), where electromagnetic induction (EMI) geophysical methods have been successfully tested by investigators for determining claypan depth and spatial extent. Consequently, near-surface geophysical methods may also supply useful information on hardpan depth and spatial extent. Three near-surface geophysical methods were therefore tested on a hardpan present in an agricultural field near Blackville, South Carolina. The three near-surface geophysical methods evaluated were; 1) apparent soil electrical conductivity (ECa) mapping of the top 0.3 m and 0.9 m of the soil profile using an on-the-go resistivity measurement system, 2) ECa mapping of the top 0.75 m and 1.5 m of the soil profile using EMI, and 3) subsurface imaging using ground-penetrating radar at three different antenna frequencies. Near-surface geophysical results were then compared to cone penetrometer measurements and analysis of soil samples to determine the strengths and weaknesses of each near-surface geophysical method for providing insight on hardpans within agricultural settings.
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Optimizing the Metalmapper for Static "Cued ID" Measurements over UXO
Authors D.D. S. Snyder and C. P. OdenThe MetalMapper is a commercially available advanced EM system that includes an array of 3 transmitter loops and 7 tri-axial receiver cubes that is used for detecting and classifying UXO. In the current instrument, the number of receivers was determined by hardware limitations (24 analog channels max), and the receivers were positioned to provide uniform coverage when deployed for mapping surveys. With support from SERDP, we have undertaken a model study aimed at answering important questions about the optimality of the MetalMapper antenna configuration when deployed for static cued ID measurements. These questions include: Is there a significant advantage to tri-axial receiver loops as compared to a single loop receiver?; Are 7 tri-axial receivers necessary or might we obtain similar performance from an array of 5 tri-axial receivers that are better positioned? Our study extends earlier studies by Grimm and Sprott (Grimm 2002) at Blackhawk Geoservices (now Zapata/Blackhawk) and Smith et al (Smith 2005) at Lawrence Berkeley Labs. Those studies have guided us during the early development of the MetalMapper and its forbearer, the AOL system. Using synthetic data sets for a conductive and permeable sphere placed at random locations beneath the MetalMapper, we show that the current MetalMapper receiver array performs better than either an array of 7 single-component (dBz/dt) receivers or an array of 5 tri-axial receivers having several different dimensions. We obtained similar performance when we tested these arrays with a second synthetic data set that better simulates a UXO. Our study also confirms empirical observations from past demonstrations of the MetalMapper that the quality of shape-based target parameters is significantly degraded when the target has a horizontal offset from the center of the MetalMapper array of more than 40cm.
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INTEGRATED, STUDENT-LED HYDROGEOPHYSICAL INVESTIGATIONS AT A SUSPECTED CENTRAL TEXAS SINKHOLE
A suspected sinkhole (Quadborder Sink) with unknown hydrogeological significance in a central Texas metropolitan area provided a research topic that was addressed by a group of graduate and undergraduate students during a semester-long hydrogeophysics class. These students designed geophysical field experiments using frequency-domain electromagnetic induction, electrical resistivity, groundpenetrating radar (50 and 100 MHz), microgravity, and seismic refraction methods, acquired data at the field site over multiple weekends, processed data, presented field results in weekly classes, and integrated results in a jointly written, comprehensive class report. Each of the methods provided useful information to establish the likely presence of a sinkhole and its lateral extent, the thickness and lithologic character of the sinkhole fill, the possible presence of an underlying shallow void in this karstic area, likely areas of preferential hydrologic recharge, and the character of the shallow interface between clastic fluvial and lacustrine fill and carbonate bedrock. Strengths of the approach included application of multiple geophysical methods to a single hydrogeologic problem of concern to residents and a local governmental agency. Weaknesses included the inability to spend adequate time and effort to apply advanced processing steps to the datasets acquired using different methods and maximize the benefits of multiple geophysical approaches to a common problem.
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FULL WAVEFIELD SEISMIC ANALYSIS BENEATH THE A.V. WATKINS DAM, UTAH
A reliable measure of seismic properties as a function of depth is important to the Bureau of Reclamation’s comprehensive and accurate appraisal of site response (ground motion and acceleration) along specific segments of A.V. Watkins Dam in Box Elder County, Utah. A series of seismic data sets were acquired along coincident profile lines at the downstream toe of A.V. Watkins Dam. Three distinctly different surveys, each tailored to a different portion of the wavefield, were optimally acquired and processed. Two three-quarter-mile-long high-hazard portions of the embankment were targeted for this study.
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EARTHEN EMBANKMENT DAM INSPECTION USING ELECTRICAL RESISTIVITY TOMOGRAPHY
Authors Jared Case, Craig Hickey and Gregory HansonTwo quarter scaled experimental embankment dams were constructed at the USDA ARS Hydraulic Engineering Research Unit in Stillwater, Ok. These dams were constructed with two internal compromised zones that would be susceptible to seepage and piping. The zones consist of a sandy region and a region compacted at a lower moisture content. Preliminary measurements were performed on the dam during construction to gain initial resistivity of the zones and the dam body. These measurements showed that there was a good contrast between the zones and the dam body. This will make the anomalous zones easily visible in our initial tomograms. Electrical resistivity surveys have been performed on the embankments for over the course of a year to monitor changes in electrical signatures of the dam due to environmental changes and cyclic loading and unloading of the reservoir. Also forward modeling was performed using the EarthImager 2D imaging software. These models will help predict changes in the resistivity of these zones due to infiltration of water from the reservoir or from rainfall and also due to the removal of fines/clay content during piping. Field measurements are then going to be compared to the forward model predictions. [This research was funded by the Department of Homeland Security-sponsored Southeast Region Research Initiative (SERRI) at the Department of Energy’s Oak Ridge National Laboratory.]
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USING ERT TO LOCATE A HISTORICAL MINE TUNNEL
Authors Douglas LaBrecque, Russell Brigham, Brady Flinchum, Nicole Pendrigh, Phil Sirles and Paul IvancieExisting tunnels in historical mine sites often serve as conduits for acid mine drainage thus, delineating them can be important in remediating these sites. In a recent field study, electrical resistivity tomography was successfully used to locate a tunnel in a former mining district in the Rocky Mountains of Colorado. Prior to the ERT survey, a combination of historical mine data and surface geophysical surveys were used to find the approximate location of the tunnel. This culminated in drilling of boreholes on both sides of the location of the tunnel. Cross-borehole ERT was then used to provide a final estimate of the tunnel location. Surface-to-hole ERT surveys were conducted near a second, known portion of the tunnel to determine the feasibility of finding the tunnel using only a single borehole. In addition to the ERT surveys, an electrode was placed inside the entrance to the tunnel and used to perform mise-a-la-masse (MALM) surveys with receiving electrodes at the surface and in the borehole.
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INVESTIGATING THE SPECTRAL INDUCED POLARIZATION RESPONSE OF A CRUDE OIL SPILL SITE UNDERGOING INTRINSIC BIOREMEDIATION
Authors Farag Mewafy, Estella Atekwana, Dale Werkema, Dimitris Ntarlagiannis, Lee Slater and Andre RevilThe spectral induced polarization (SIP) technique holds great promise for detecting oil contaminated sites due to its sensitivity to physicochemical processes occurring during intrinsic bioremediation. Many studies have investigated the SIP response due to oil contamination; however, the mechanisms resulting in the SIP response resulting from oil contamination are not completely understood. An oil spill at Bemidji, MN occurred in 1979, when a high pressure crude oil pipeline ruptured, releasing 1,700,000 L of oil.
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CHEMOMETRIC DESIGN OF EXPERIMENTS APPLIED TO PHYSICOCHEMICAL AND GEOPHYSICAL LABORATORY EXPERIMENTS
By Dale WerkemaChemometrics design of experiments and analysis applied to physicochemical and geophysical laboratory experiments potentially enable more robust experimentation. Chemometrics extracts information from empirical chemical systems, physical systems, industrial processes, or other experiments. It is essentially an interdisciplinary science incorporating applied multivariate statistics and mathematics with the goal of exploring problems in chemistry, biology, engineering, industrial processes, and the medical fields, for example. This presentation presents results from two laboratory geophysical experiments performed to evaluate the physicochemical response to various experimental treatments in an aqueous solution and a sand matrix.
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GEOPHYSICAL INVESTIGATION AT THE PROPOSED CONCENTRATOR AREAS, IN AN IMPORTANT PROJECT IN SOUTH OF PERU, USING MEASUREMENTS OF COMPRESSIVE (P) AND SHEAR (S) WAVES.
More LessBefore evaluating the final location of the future facilities we need to characterizer and describe the soil foundation. One of the studies that we development to support our future decisions is the measurements of compressive (P) and shear (S) waves. The investigation of the ground site (in the Concentrator Areas) was conducted through geophysical testing using the seismic refraction test method, and surface wave measurement methods such as the multichannel analysis of surface waves (MASW) method and the multichannel array of microtremors (MAM) method. From the interpretation of the velocity of compressive (P) and shear (S) waves, the thickness and stiffness of soil layers at the project site were determined. The geophysical investigation was carried out to estimate the soil profile in the foundation areas of the projected facilities, through the determination of the velocity of propagation of both P (Vp) and S (Vs) waves in the ground, using surface seismic refraction tests for P-wave measurements, and MASW/MAM tests for Swave velocities.
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20+ YEARS OF EXPERIENCE, OBSERVATIONS, AND LESSONS LEARNED OF WITH THE MODERN DIGITAL ACOUSTIC TELEVIEWERS, AND THEIR IMPACT ON DATA QUALITY AND WITH FOCUS ON PRODUCTION MINING APPLICATIONS. PART I – BASIC THEORY, APPLICATIONS, PROCESSING STEPS, RESOLUTIO
Authors Robert Crowder and John StowellThe modern slimhole digital acoustic televiewer has been applied for the last 20+ years for a variety of applications from ground water to rock mass evaluation to casing inspection. After an extended period of limit application, the technology is now widely accepted and hundreds of tools are in the market place and routinely being applied by service and in-house groups around the world. During this time, a number of lessons have been learned and observations noted. Understanding and learning from these observations and details are critical in insuring highest quality and correct application of the data. Despite the great advances in instrumentation, lack of training with resulting mistakes in acquisition, common misconceptions and errors in the processing and interpretation of the data lead generate bad data that is frequently not identified.
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PART II – DATA QUALITY ISSUES, SOURCES OF ERROR, NUMEROUS DATA EXAMPLES, AND GUIDELINES FOR QC.
Authors John Stowell and Robert CrowderEnhancements in acquisition and processing software allow many people to collect acoustic televiewer data with minimal training. However, these tools are extremely sophisticated and flexible and it is easy to generate data with significant error. These errors can occur in data acquisition from misunderstanding image orientation scheme and requirements; use of magnetic centralizers or housing; use in a magnetic environment; from in correct tool sample decisions and logging too fast. They can also occur from tool orientation sensor or software failure. The most common issues with data quality are tool centralization and borehole fluid conditions and incorrect presentation scales. Accessory logs accompanying the image data can frequently be used to identify these data issues.
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QUANTITATIVE ANALYSIS OF MAGNETIC ANOMALIES IN THE EASTERN MEDITERRANEAN: A REVIEW
More LessMagnetic anomalies observed in the Eastern Mediterranean are characterized by strongly inclined magnetization (about 45o). It should be noted that the method “reduction to pole”, which often are used in the conditions of inclined magnetization, is limited by situation when all disturbing bodies in the studied area are magnetized parallel to the geomagnetic field and have subvertical dipping. Only in this case the magnetic fields recalculation will be correct and the obtained graphs will be symmetric and then may be used for further interpretation by conventional methods. Other disturbing factors are rugged terrain relief, unknown level of the normal magnetic field and complex geological media.
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Electrical Geophysics for Assessing Permafrost Conditions along Highway Infrastructure
Authors G.A. Oldenborger, C.W. Stevens and S.A. WolfeThe Yellowknife region, part of the Slave Geological Province, falls within the extensive discontinuous permafrost zone in Canada. A large degree of economic development is routed through Yellowknife from the mineral-rich North Slave. Despite the mineral-rich nature of this region, surficial sediment maps and knowledge of permafrost conditions are only now being established in detail. Permafrost and associated ground ice can significantly affect land-based infrastructure through influence on ground stability and drainage patterns. As such, geoscience information contributing to permafrost characterization is critical for understanding risks to roads which are vital to Northern economic development. The 100 km stretch of the chip-sealed Highway 3, west of Yellowknife, presently experiences instabilities including settlement, heave, and rotations related to transitions between differing terrain and drainage conditions within the discontinuous permafrost. Electrical resistivity data were collected over identified terrain types, and across potential terrain transitions and thaw fronts based on the hypothesis that permafrost distribution and conditions vary with terrain type. Processed resistivity models indicate distinct electrical signatures for most of the terrain types which would allow for extensive geophysical characterization complimentary to landscape mapping, temperature data and shallow boreholes. The resistivity models also exhibit features indicative of the base of ice-bonded permafrost, ice-rich sediment and thaw zones, which can be correlated with terrain features of sediment type and drainage. Observed resistivity anomalies indicate thaw zones related to existing and past road infrastructure, which help in understanding conditions causing highway subsidence.
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BOREHOLE IP RESPONSE IN TRADITIONAL AND NON-TRADITIONAL TARGETS USING VARIABLE INJECTION TIMES
Authors Robert Crowder, John Stowell and James LoCocoA borehole IP probe with fully digitized waveforms has been tested in both hard rock and sedimentary lithologies. In many cases, the response has been as expected, and the results are presented for measurements made in pyritic and sulphide dominated targets. Field data sets have led to questions regarding depth of investigation of the multi-electrode device, and whether different chargeabilities should be expected, based on geometrical considerations. Possible mathematical solutions to this apparent behavior are discussed.
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ALIS- GPR 3-D IMAGING FOR HUMANITARIAN DEMINING
Authors Motoyuki Sato, Kazunori Takahashi and Yuya YokotaHumanitarian demining is very important issue not only in mine affected courtiers but also for the courtiers which are technically, politically and financially supporting the mine affected courtiers. In order to achieve higher efficiency of the mine clearance operation, new technologies can significantly contribute to the societies. Since 2002, Tohoku University, Japan has developed a sensor system “ALIS” for humanitarian demining. ALIS is a hand-held dual sensor, which combines an electromagnetic induction sensor (EMI) and a Ground Penetrating Radar (GPR). We need to establish a high-resolution, high-precision GPR system for this task. In order to reconstruct 3D GPR image with high resolution, the position tracking of the antenna is a key issue. We have developed a sensor tracking system with CCD camera and image processing. Although this is a hand-held system, GPR data can be processed with location information, therefore we can obtain 3-D GPR image on site. We think it is a quite unique system, and validated its potential in real operations. We have tested ALIS in Cambodia and found that it can eliminate more than 70% metal fragments. Since 2009, 2 sets of ALIS have detected more than 80 anti-personnel mines, and cleared more than 137,000m2 in Cambodia.
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