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21st EEGS Symposium on the Application of Geophysics to Engineering and Environmental Problems
- Conference date: 06 Apr 2008 - 10 Apr 2008
- Location: Philadelphia, USA
- Published: 06 April 2008
1 - 20 of 136 results
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Geophysical Surveys To Characterize The Hydrogeology Of The Arbuckle Uplift, South-Central Oklahoma
Airborne and ground electrical resistivity and magnetic surveys as well as ground gravity measurements have been conducted to map the subsurface geologic and hydrologic features of the
Arbuckle Uplift. The main target of these investigations is the Paleozoic Arbuckle-Simpson aquifer and the surrounding stratigraphic units of the Arbuckle Uplift in south-central Oklahoma. In March, 2007, helicopter-borne electromagnetic (resistivity) and magnetic survey was flown of four areas with distinctly different geology were flown using measurement systems. The airborne resistivity measurements were made at six different frequencies ranging from 400 Hz to 115,000 Hz which provided a depth of penetration from a few meters to about 80 m. Ground resistivity profiling has been conducted in several areas of the uplift for subsurface resistivity imaging. Two of the resistivity profiles are in the area encompassed by the airborne survey. Total field magnetic and high precision location (GPS and laser altimeter) measurements were also made as part of the airborne survey. Ground gravity and magnetic profiling was also conducted to refine location of structures in specific areas. The geology of the study area consists of dolomitic limestone (Arbuckle and Simpson Groups) that generally lies in fault contact with younger Paleozoic clastic and carbonate rocks. The formational units are gently dipping except on the flanks of the uplift. The geophysical maps, resistivity depth sections, and interpreted cross sections from the magnetic and gravity data are being used to improve the geologic mapping and better define hydrologic features of the area.
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Geophysical Investigation Of The Fresh-Saline Water Interface In The Coastal Area Of Abergwyngregyn
Authors Ismaila B. Obikoya and James D. BennellThe importance of the study of saline/fresh water incursion cannot be over-emphasized. Borehole sampling has been extensively used, but it is intrusive, quite expensive and time consuming.
Electrical resistivity and electromagnetic techniques have proved successful in groundwater studies since geologic formation properties like porosity and permeability can be correlated with electrical conductivity signatures. Non-intrusive surface geophysical mapping comprising electrical resistivity and electromagnetic methods has been employed to investigate freshwater intrusion and delineate the fresh-saline water interface at the inter-tidal area of Abergwygregyn, North Wales, United Kingdom. Frequency Domain Electromagnetic Profiling and Constant Separation Traversing were used to produce 2-D images and contour plots enabling the identification of freshwater plumes onshore and in the central parts of the study area. Ground truth methods comprised chemical analyses and detailed, point specific information on the stratigraphy. The freshwater intruding from the coastal area appears to be pushing
the saline-water further offshore due to the high piezometric head caused by the mountains and hills of Snowdonia adjacent to the study area. The fresh/saline water interface correlates quite well with previous studies carried out in the area. On the basis of the results of the resistivity and conductivity geophysical investigations the freshwater plumes and fresh/saline water interface in the study area were effectively identified and delineated..
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New Discovery Of Important Archaeological Artifacts From Shallow Seismic Observations At The Ancient Hierakonpolis Temple-Town Site In Upper Egypt
Authors Shelton S. Alexander, Elizabeth Walters and Recep CakirProminent high-velocity, high-frequency signals from very shallow depths were observed along some of the numerous seismic refraction profiles run within the perimeter wall of the ancient Hierakonpolis Temple-Town in Upper Egypt. These anomalies are characterized by laterally continuous high-frequency (200-300 Hz) arrivals with velocities comparable to or exceeding the deeper water table refraction velocities. These anomalous zones are imbedded in the 1 to1.5 m-thick upper layer of unconsolidated, air-filled sediments that have extremely low velocities and very low Q. The considerable spatial extent of these shallow anomalous zones was determined from sets of crossing refraction profiles.
Subsequent excavations (2001, 2005-6) at two locations in the western portion of the site revealed the presence of a zone of closely spaced artifacts (dense in potsherds and stone fragments) that revealed new evidence of occupation in the ancient town as early as Dynasty I, c. 3200 BCE. In the northwest excavation an ‘in situ’ deposit of special pottery lay next to a bench, a large block of dressed limestone. Further to the north, layered occupation suggests a secular context with pottery of Dynasty II, 2900 BCE and a new early date, terminus ante quem, for the accompanying figurines, thus far exclusive to two temple sites in southern Egypt. Further excavations of the mapped anomalous zones are expected to provide many additional artifacts not previously found at the site.
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Use Of Masw For Geotechnical Site Characterization Using Corrected Triaxial Geophones
Authors D. Lane, W. Ragland, R. Williams and D. PenumaduA comparison of 3-component surface wave data to uncorrected vertical geophone records at a soft soil site on the flood plain of the Tennessee River is presented. The data is collected using 10 Hz vertical and 4.5 Hz horizontal geophones, which are calibrated against a reference piezoelectric accelerometer and servo-hydraulic testing system. The records from the field associated with MASW survey are corrected for the mechanical response of the geophones using experimentally-determined transfer functions. MASW data are obtained using 1 m geophone spacing with a 22 kg weight dropped from a height of 1.5 m. It is expected that the vertical and radial (horizontal toward the source) geophones will record Rayleigh waves, but the horizontal transverse geophones should not record a Love wave, because it is not generated efficiently by a vertical impact on laterally homogeneous strata. Contrary to expectations, both Rayleigh and Love wave dispersion curves are observed. Rayleigh waves appeared on the vertical and radial geophones, but their dispersion curve cutoff at frequencies lower than approximately 27 Hz. Love wave dispersion was observed on the transverse horizontal geophones at frequencies below 27 Hz. Hypothetically, the Love waves could have been caused by scattering related to small scale in heterogeneities in the soil.
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Preliminary Analysis Using Surface Wave Methods To Detect Shallow Manmade Tunnels
Authors Niklas H. Putnam, Ali Nasseri-Moghaddam, Oleg Kovin and Neil L. AndersonMulti-channel Rayleigh wave data were acquired across a 1m diameter spillway tunnel along three parallel traverses with surface to tunnel separations of 0.90 m, 2.15 m, and 3.13 m, respectively. The data were acquired by placing a 24-channel array across the tunnel (perpendicular to the center-line of the spillway tunnel) and walking the sledge hammer source through the array starting with a far-offset of 10 m. The 4.5 Hz geophone array spacing was at 0.5 m intervals. Single shot data were analyzed to visually locate and to highlight attenuation effects associated with the tunnel. The field records were then velocity filtered in order to enhance back-scattered Rayleigh wave energy thereby allowing for visual identification of the tunnel location. The same single shot data were analyzed using the Attenuation Analysis of Rayleigh Waves (AARW) method. The intent was to demonstrate the utility of these approaches to tunnel delineation at a site where the geometry of the target and the nature of the encompassing soil was known. Electrical resistivity data was also acquired along the traverses for comparison purposes.
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Reduction Of Topography Effect In Apparent Conductivity Profiles (Em38): Application On Sambaqui Site (Shell Mound) In Santa Catarina State, Brazil
More LessModern land developments have motivated the application of geophysical methods in archaeological investigation in order to recognize hidden patterns in poorly known areas and select suitable places for excavation. Due to quick data acquisition and interpretation, low-induction EM38 measurements (conductivity and magnetic susceptibility) have been successfully applied to map fire places, burials, and concentration of ceramic materials in many Brazilian prehistoric sites. Conductivity anomalies, however, are much affected by the soil water content, which in sites with rugged topography creates a site-scale effect that masks the expression of subtle archaeological features. Here, we apply a procedure to remove the dependence of the soil conductivity with respect to the site topography by using a linear relationship determined by cross-plotting conductivity and elevation values measured in a given site. Corrected conductivity values helped us to identify regions of archaeological interest (further confirmed by excavation), which formerly were not easily recognized from crude data. This procedure has shown proved utility as an exploration tool to study sambaqui (shell mounds) archaeological sites, at the sandy coastal plain of the Santa Catarina State, in southern Brazil.
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Application Of Borehole Geophysics To Delineate Preferential Contaminant Migration Pathways In A Complex Fractured Clay/Shale Aquifer
Authors Robert J. Onderko, George Sauer and J. PetersonDuring development of a Hydrogeologic Conceptual Site Model (HCSM) for a large chlorinated solvent plume, Earth Tech determined that significant groundwater movement was occurring below auger refusal depths within a shallow fractured rock aquifer. Data was available for deeper zones, but not for the zone of interest. Earth Tech developed an approach that utilized various borehole geophysical tools to investigate this possible preferential migration pathway. A multi-phased investigation program was developed in which multiple borehole logging tools were tested to determine the suitability and the applicability of the geophysical methods to investigate the zone of interest. Once the geophysical method suite was optimized, the investigation program was streamlined. Although this investigation program developed over time, the multiple objectives of investigation remained focused on:
1. Determining the presence or absence of a significant groundwater flow horizon just below
auger refusal depths;
2. Determining the hydraulic characteristics of the system;
3. Refining the HCSM for the shallow aquifer system; and
4. Determining the extent of contamination and the effectiveness of the remedial measures that
were applied at or above the auger refusal depths at the site.
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Seismic Inversion For Geotechnical Properties Relevant To Coal Mining
Authors P.J. Hatherly, M. Urosevic and B. ZhouThe 3D seismic reflection method has an established role in Australia in mapping geological structures, faults and discontinuities that might affect the operation of an underground coal mine.
However, successful longwall mining also requires knowledge of geotechnical properties of the roof and floor strata. Most geotechnical information is obtained from core drilling, geophysical logging and underground mapping. In particular, log analysis can now be used to determine geotechnical properties of the strata through the Geophysical Strata Rating (GSR). However such “point” measurements need to be extrapolated into a full three dimensional geotechnical model for longwall mining operations. Geotechnical variability is related to lithological variations that can be inferred from high resolution seismic reflection data. Hence geotechnical variability could be studied directly from seismic data or a particular seismic attribute. Here we investigate a relationship between acoustic impedance derived from seismic data and log-derived GSR values to produce a 3D geotechnical model.
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Using Electrical Resistivity To Model Channel Seepage From Irrigation Canals
Authors Jacqui Watt, Shahbaz Khan and Akhtar AbbasThere is increased pressure on water managers, as a whole, to improve their water use efficiency. In irrigation areas, a major aspect of water usage is the seepage of water from irrigation
canals. In Australia significant amounts of water may be lost from irrigation canals through seepage and evaporation. The methodology applied for this paper uses the measurement of the soil resistivity to aid water managers in the determining the quantity of seepage from irrigation canals. Initially, the resistivity of the irrigation canal bed was measured, followed by soil sampling
and analysis. The spatial and resistive variability was established from the resistivity measurements and was inputted into the HYDRUS 2D/3D model according to resistive groupings. The soil
analysis resulted in the particle size, bulk density and hydraulic conductivity and these were inputted for the respective soil group into the model. The modelling was conducted over 30 years and the results determined the soil type plays an initial role in the seepage from irrigation canals. However, once the profile becomes saturated it does not matter which soil types are present. The method outlined employs the rapid assessment technique of resistivity to improve the understanding of seepage of irrigation canals.
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The Multi-Channel Analysis Of Surface Waves (Masw) Method As A Tool For Ground Improvement Certification
Authors Robert W. Burke and Nick B. SchofieldGround improvement techniques such as High Energy Impact Compaction (HEIC) of fill requires testing to allow certification of the compaction process. HEIC is often performed on mixed, unengineered and rock fill layers up to 8m in thickness. Experience has shown that conventional geotechnical testing techniques, including nuclear densometer tests, penetration tests (CPTs, SPTs, DCPs) and plate load tests have great limitations in testing such fill profiles. The MASW method is a useful tool for assessing ground improvement as it addresses many of the problems associated with more conventional tests. The MASW method has been used by Black Geotechnical on ground improvement projects since February 2006. The ground improvement methods often create a very stiff raft of fill over soft natural soils that become gradually stiffer. This very stiff-soft-stiff profile is not optimal for MASW as Lamb waves can be easily introduced and it is often difficult to define the base of a soft layer when there is a gradual transition to stiffer soil. Lamb waves, modes and artifacts contribute to making the use of MASW as an absolute stiffness measurement difficult at times. Pre and post compaction MASW surveys enable the method to be used as an effective relative measure of ground improvement.
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Gravity And Magnetic Data Analysis To Detect The Basement Rock Structure At Sungai Pahang Delta Area
Authors M.N. Khairul Arifin, Mohd N. Nawawi and T.H. Zuhar ZahirThe objective of this study is to model and establish a geological structure, mainly the basement rock, using potential field analysis. Two potential field methods, i.e. gravitational field and magnetic field were used in this study. The coastal margin sedimentary basin at Sungai Pahang Delta in Pekan, Pahang was chosen as the study site. This is to identify the basement rock structure due to delta development such as fault zone evolution, basement expansion and compaction. The data were interpreted both qualitatively and quantitatively. The qualitative interpretation is based on anomalies on the contour maps, and the quantitative interpretation is based on data modeling. There is good correlation between the gravitational and the magnetic field methods since the same features are found at the same locations. The result from the magnetic field method shows that the basement rock contains extended basalt intrusion. However, the gravitational data show a more localized intrusion and the presence of a metamorphism contact zone.
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3-D Resisitivity Survey Downstream A Landfill In Brazil – Preliminary Results
A contaminated site downstream a landfill in Brazil was investigated using a 3-D resistivity imaging technique. The purpose of this investigation was to detect and delineate the contamination plume produced by the wastes and to obtain detailed information about the affected area. The data set consisted of a series of parallel electrical profile data acquired with the dipole-dipole array, and was inverted as a complete 3-D survey. This acquisition technique is less troublesome than a complete 3-D survey, and despite of yielding a poorer resistivity model, the resulting model still provide the major resistivity contrasts and enables a tridimensional picture of the main features. In this work we present depth slices and individual 2-D profiles, from the models obtained by the 2-D and 3-D least-squares smoothness constrained inversion technique. The results suggest the presence of a contamination plume and their preferential path, which is in good agreement with chemical analysis and underground water flow data. The 3-D technique reveals to be efficient in waste disposal sites investigations, and should be taken into account when choosing the investigation technique to be used in complex and contaminated sites.
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Geophysical Analysis Of The Salmon Peak Formation Near Amistad Reservoir Dam, Val Verde County, Texas, And Coahuila, Mexico, March 2006, To Aid In Piezometer Placement
Authors Gregory P. Stanton, Wade H. Kress, Andrew P. Teeple and Allan K. ClarkA reconnaissance-level geophysical study was conducted at Amistad Reservoir Dam to provide technical assistance for the horizontal and vertical placement of piezometers on the eastern embankment of the dam. The study involved an integrated approach using surface and borehole geophysical methods. In the western embankment investigation, geological and geophysical characteristics that indicate relatively large water-yielding properties of the Salmon Peak Formation were identified. The directcurrent (DC) resistivity method was selected as the surface geophysical reconnaissance technique to correlate relatively large water-yielding properties of the Salmon Peak Formation, identified from analysis of borehole geophysical logs, with variations in subsurface resistivity. The dipole-dipole array and the reciprocal Schlumberger array were selected as the most applicable DC resistivity arrays. Two resistivity units were identified in both the dipole-dipole array data and the reciprocal Schlumberger array data along DC resistivity profiles on both embankments. Resistivity unit 1 generally is of relatively
low resistivity, ranging from 45 to 150 ohm-meters compared with resistivity unit 2, which ranges from 120 to 345 ohm-meters (depending on the DC array type). The presence of mapped sinkholes in the reservoir north of the western embankment study area and the zone of increased water content (as indicated by zones of low neutron log count rates in nearby piezometers) leads to the conclusion that resistivity unit 1 is a preferential flow path where surface water from Amistad Reservoir is forced into the ground-water system (because of increased head from the reservoir). In the eastern embankment investigation, trends in the spatial distribution of sinkholes and the occurrence of weathered zones were identified from geologic descriptions of cores. The correlation of surface geophysical DC resistivity, historical lithologic data, and general trend of documented sinkholes along the eastern end of the eastern embankment profile were used to justify further exploration (drilling of piezometers) in the eastern expression of resistivity unit 1. The spatial location of the piezometers and the screened intervals were selected to best match the locations of the screened intervals of the western embankment piezometers. Six piezometers were installed on the eastern embankment and logged using borehole geophysical
techniques. Resistivity units 1 and 2 in the DC resistivity profiles generally correspond with low and high resistivity zones, respectively, on the normal and lateral resistivity logs collected in the nearby piezometers at the time of installation. Because the project was a reconnaissance-level study, the report is not a comprehensive geologic or geophysical evaluation of the study area.
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Correlation Between Geoelectric And Hydrodynamic Parameters Of Aquifers: Transversal Resistence Versus Transmissivity In Bebedouro’S Region, Southeast Of Brazil
Authors Ivan M. Carlos and Vagner R. ElisEstimates of hydrodynamic parameters from geoelectrical data settings play an important role in hydrogeology studies. In such context, correlation between transversal resistance (RT) and
Transmissivity (T) has been considered a usefu l tool for evaluation of aquifer hydrodynamic characteristics. Ten Vertical Electrical Soundings (VES) using Schlumberger configuration close to
tubular wells were carried out in Bebedouro’s region (São Paulo state, Brazil) aiming at getting RT. Through a representative average value of hydraulical conductivity (K) obtained from Adamantina Formation, it was possible to estimate T parameter that in turn allowed a RT x T relationship analyzed by linear regression with correlation coefficient R = 0.9. In order to access the reliability of such methodology, nine additional VES’s were carried out for specific points placed at the southern region of the micro basin, for which we had no available information provided by stratigraphic studies of tubular wells. Furthermore, values were also estimated for RT and T parameters plotted against results provided by the first 10 VES’s. Results were considered satisfactory validating the method applicability.
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Common Misconceptions About Capacitively-Coupled Resistivity (CCR) What It Is And How It Works
More LessCapacitively-coupled resistivity imaging systems have been available as commercial geophysical instruments for over eight years and have seen increased acceptance in near-surface engineering applications (Ball 2006), (Garman et. al. 2004). In order for a geophysicist to determine whether a capacitively-coupled resistivity meter would be appropriate for a particular application requires a fundamental understanding of the technique and its relative capabilities and limitations in relation to other near-surface imaging tools. The underlying principles of the technique are outlined in the existing literature (Kuras et. al. 2006), (Timofeev et. al. 1994). This paper is intended to point out and discuss some of the most common misconceptions about capacitively-coupled resistivity (CCR) and to review practical considerations in basic survey fundaments compared to other resistivity measuring techniques. The Geometrics OhmMapper TRN is a commonly used CCR instrument, using a dipole-dipole configuration, and will be the base of reference for this paper (Figure 1).
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Application Of Surface Geophysics For Providing A Detailed Geotehcnical Assessment Of A Large Resort Development Site In Anguilla, Bwi
Authors Sandy Nettles, Bret Jarrett and Eric C. CrossN.S. Nettles & Associates (NSN) has completed extensive geophysical investigations that have guided engineering practices for a resort community in Rendezvous Bay, located in Anguilla, BWI. Diverse technologies were utilized, including; Multi-Electrode Resistivity (MER), Continuous Resistivity Profiling (CRP), and Multichannel Analysis of Surface Waves (MASW). Resistivity
techniques allowed for differentiation of geologic units and the identification of karst features and subsurface anomalies. To further determine sub-surface density variations, MASW transects were performed. This multi-method approach provided confidence in location of anomalies that were later targeted for drilling practices. Additionally, a stagnant salt pond was mapped with MER and CRP for the purposes of determining sediment thickness overlying rock and the competency of the limestone. This provided accurate volume calculations for dredging operations, the first phase in the transformation of the hypersaline pond to a functional marine habitat. Specifications were designed for a series of horizontal flushing channels connecting the salt pond with Rendezvous Bay. Cone Penetration Testing was utilized and geologists supervised the drilling of rock cores and Standard Penetration Test Borings to investigate anomalies and calibrate the geophysics. Results have provided the geologic framework for engineers to implement a successful construction strategy for the Rendezvous Bay Resort.
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Wireless Sensor Networks In Geophysics
Authors Charles P. Oden, Gary R. Olhoeft, Dan P. Jones and Stan S. SmithA significant expense in geophysics is physically collecting data – especially data sets involving multiple field deployments. Limited site access due to hazards, weather, legal issues, etc. may also limit data collection. Consequently, many datasets have too few measurement types, too little spatial coverage, and too little temporal coverage which results in increasing uncertainty and ambiguity in our problem solutions. Wireless sensor networks are an emerging technology that addresses many of these issues. Today’s wireless sensors are small (typically a few centimeters on a side), can be left in the field for long periods of time without servicing, and are inexpensive enough to be considered disposable. Wireless sensors are a combination of several recent technological advances including inexpensive miniature sensors, low power radio telemetry, time synchronization techniques, localization techniques (spatial awareness), and energy harvesting methods. Single chip sensors are available for measuring electric, magnetic, and electromagnetic fields, temperature, pressure, mechanical displacement,
chemistry, attitude, and more. These sensors can be used in several geophysical methods including seismic, DC resistivity, induced polarization, EM induction, magnetometry, and ground penetrating radar (GPR). The small size of these sensors allows multiple types of measurements to be incorporated in a single sensor node. Examples of the wireless sensor network applications include the long term monitoring and assessment of infrastructure, investigations in ecology and environment, tracking fluids or contaminant migration, and resource and exploration studies. In this paper, we review some of the capabilities and limitations of current wireless sensor network technology.
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Exploring Masw Surveys With Random Receiver Arrays For Future Lunar Exploration
Authors Prasanta M. Yeluru, Gregory S. Baker, Choon B. Park and Larry A. TaylorUnderstanding the physical and engineering properties within the upper 30m of the Lunar subsurface will be critical as Lunar exploration advances and deployment of large structures or landing of large spacecraft on the surface becomes necessary. Advances in multi-channel seismic acquisition, either active or passive, in acquiring reliable 1-D or 2-D shear wave velocity profiles have greatly improved our ability to determine the engineering properties (e.g. Poissons ratio) of shallow subsurface, especially when using the multi-channel analysis of surface waves (MASW) technique. A new scheme of using randomly distributed geophones (likely deployed from a mortar-type device) instead of a conventional linear array is necessary for Lunar exploration because of the logistical constraints in arranging a linear or circular array robotically. This random geometry is also evaluated (a) for validity or any potential improvements in the resolution of the dispersion image and (b) as more accurate method for assessing azimuthal variations in the subsurface geology. Results indicate that the random array geometry can be used for MASW survey to produce robust dispersion curves that can be used for the subsequent analyses for the subsurface engineering parameters.
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Passive Electrical Monitoring Of Aerobic And Anaerobic Processes Using Septic Systems As An Analog
More LessUsing anaerobic and aerobic septic systems as analogs, we examined whether the passive electrical potential (SP) method can be used to detect and monitor shallow biochemical reactions. High-resolution SP surveys conducted with nonpolarizing electrodes can reliably detect potential differences as small as a few mV over relatively small areas, suggesting that the technique can find wider use in monitoring biodegradation processes, mapping effluent plumes, and identifying local preferential infiltration areas. Surface SP measurements appear to respond to changes in the oxidation-reduction potential in shallow reactors, correlating best with changes in dissolved oxygen concentration and measured electrical potential within the subsurface reactors. Among the available electrode choices, including those made of carbon, low-grade steel, stainless steel, and copper, only nonpolarizing electrodes such as the copper–copper sulfate types provide the measurement stability necessary to achieve high-resolution results.
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Seismic And Geotechnical Site Characterizations At Four Earthquake Strong Motion Sites In Washington State
Authors Recep Cakir, Timothy J. Walsh and Trevor ContrerasAs part of on going program for generating maps addressing geologic site effects in Washington, the Washington State Department of Natural Resources (DNR), Division of Geology and Earth Resources (DGER) drilled 30-meter-deep geotechnical boreholes at four strong-motion sites operated by the Pacific Northwest Seismic Network (PNSN). Invasive (soil sampling, Standard Penetration Test (SPT) and downhole seismic) and noninvasive (Multichannel Analysis of Surface Waves, (MASW)) methods were used to determine shear-wave velocity profiles, specifically for the top 100 feet of soil column, at each of these strong motion sites. The boreholes were logged for visual soil classification and SPTs, and selected soil samples were tested in the laboratory to obtain plasticity and gradation values. In addition, S-and P-waves generated at the surface were received by a 3-component geophone placed at 1-m intervals in each borehole. Then the borehole sites were later surveyed by using MASW method to estimate the Vs profiles at each borehole site. The MASW survey shows a very good correlation with the downhole S-velocity profiles. SPT blow counts are consistent with soil conditions in the Puget Sound area. Site classes E, D-E, D, C-D and C, as described in the International Building Codes (IBC 2006), were determined by using average shear-wave velocities and SPT blow count values to 30 meters (~100 feet) of soil column of the four boreholes. An updateable geospatial database incorporating shear-wave data and velocities, borehole geotechnical information (soil samples and their laboratory tests, SPT blow counts, etc.) will be generated and periodically updated. This database will directly be available through the DGER‘s interactive mapping service for end users such as federal and local government agencies, urban planning and emergency response groups and seismic networks, such as PNSN.
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