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- CGISS Publications and Presentations (8)
- Geosciences Faculty Publications and Presentations (3)
- Bulletin of the Mineral Research and Exploration (1)
- Dartmouth Scholarship (1)
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- Geosciences and Geological and Petroleum Engineering Faculty Research & Creative Works (1)
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Articles 1 - 23 of 23
Full-Text Articles in Geophysics and Seismology
Evaluating The Sensitivity Of Crustal Deformation To Bedrock Hydrology In A Mountain Watershed, Brett J. Oliver
Evaluating The Sensitivity Of Crustal Deformation To Bedrock Hydrology In A Mountain Watershed, Brett J. Oliver
Graduate Student Theses, Dissertations, & Professional Papers
We evaluate the sensitivity of Earth's elastic deformation to groundwater hydraulic diffusivity using coupled groundwater and elastic deformation models. Seasonal changes in terrestrial water storage cause deformation to the Earth’s crust and deeper interior that is within the observational capacity of GPS instruments. We couple finite difference groundwater simulations with geodetic forward models of crustal displacement to investigate the ability of geodetic deformation to constrain bedrock hydrologic properties. We use MODFLOW-2005 to simulate seasonal changes in groundwater flow and storage, and then use the LoadDef elastic deformation model to forward model surface displacement caused by the change in terrestrial water …
Reprocessing Groundwater Resistivity Surveys In The Lower Mesilla Basin, New Mexico, And Texas, Leslie Bernal
Reprocessing Groundwater Resistivity Surveys In The Lower Mesilla Basin, New Mexico, And Texas, Leslie Bernal
Open Access Theses & Dissertations
The Mesilla Basin is part of the Rio Grande Basin System. Its northern boundary is definedby the Doña Ana Mountains in New Mexico and to the south by Sierra San Blas, Sierra Almirez, and Sierra La Candelaria in Mexico, where the basin changes its name to Conejos-Médanos. It supplies water for irrigation and public use to the cities of Las Cruces, NM, El Paso, TX, and Ciudad Juárez, Mexico. The southern part of the basin in the U.S. territory, known as the Lower Mesilla Basin, is bounded to the east by the Franklin Mountains, to the west by the Potrillo …
Groundwater Storage Loss Associated With Land Subsidence In Western United States Mapped Using Machine Learning, Ryan G. Smith, Sayantan Majumdar
Groundwater Storage Loss Associated With Land Subsidence In Western United States Mapped Using Machine Learning, Ryan G. Smith, Sayantan Majumdar
Geosciences and Geological and Petroleum Engineering Faculty Research & Creative Works
Land subsidence caused by groundwater extraction has numerous negative consequences, such as loss of groundwater storage and damage to infrastructure. Understanding the magnitude, timing, and locations of land subsidence, as well as the mechanisms driving it, is crucial to implementing mitigation strategies, yet the complex, nonlinear processes causing subsidence are difficult to quantify. Physical models relating groundwater flux to aquifer compaction exist but require substantial hydrological data sets and are time consuming to calibrate. Land deformation can be measured using interferometric synthetic aperture radar (InSAR) and GPS, but the former is computationally expensive to estimate at scale and is subject …
Submarine Groundwater Discharge In The Southern Chesapeake Bay: Constraints From Numerical Models, Charles Louis Carlson
Submarine Groundwater Discharge In The Southern Chesapeake Bay: Constraints From Numerical Models, Charles Louis Carlson
OES Theses and Dissertations
Terrestrial and oceanic forces drive fluid flow within the coastal zone to produce submarine groundwater discharge (SGD). Groundwater flowing from the seabed serves as a significant pathway for contaminants and nutrients, producing an active biogeochemical reaction zone. In order to quantify the importance of SGD in geochemical and hydrologic budgets for the lower Chesapeake Bay, three coastal Virginia transects (southern Eastern Shore, Lafayette River, and Ocean View beach) with different topographic gradients were modeled using similar boundary conditions and consistent treatment of hydrogeologic layers. A sensitivity study was performed on the variables of recharge rate, seawater density, and hydraulic permeability. …
Hardbottom Characterization And Relationship To The Geologic Framework In Long Bay, South Carolina, Cathryn J. Wheaton
Hardbottom Characterization And Relationship To The Geologic Framework In Long Bay, South Carolina, Cathryn J. Wheaton
Electronic Theses and Dissertations
Hardbottom seafloor is a common element among sediment-starved portions of the inner continental shelf along the U.S. Atlantic margin. These areas are characterized by indurated sediment surfaces that are heavily altered by biological and physical processes. Long Bay, in northeastern South Carolina, offers ideal environmental conditions for hardbottom exposure with only patchy Holocene sand deposits, interspersed with extensive hardbottom areas. Here we use high-resolution multibeam bathymetry, CHIRP subbottom profiling and electrical resistivity data, along with surficial sediment samples, hardbottom thin sections, and water column radioisotope (radon-222) analysis to investigate the origin and geologic framework of a region of hardbottom seafloor …
Characterizing Subsurface Void Spaces And Water Distribution And Flow Patterns In Cave Hill Karst Using Resistivity, Jacob A. Gochenour
Characterizing Subsurface Void Spaces And Water Distribution And Flow Patterns In Cave Hill Karst Using Resistivity, Jacob A. Gochenour
Senior Honors Projects, 2010-2019
Describing the distribution of groundwater is essential in understanding the evolution of geomorphologic features in karst topography. Electrical resistivity allows us to find a model of subsurface distribution of resistivity that enables the visual recognition of groundwater and void spaces. The purpose of this research is to implement electrical resistivity to describe the spatial relationship of groundwater and karstic features at Grand Caverns National Natural Landmark, Grottoes, Virginia. Two locations of interest, a karstic swale and sinkhole area, were identified for the deployment of electrical resistivity. Both, dipole-dipole and Schlumberger arrays were collected for each deployment. A total of ten …
Assessment Of Metal-Metalloid Content Using Geostatistical Methods In Groundwater Of Karabağlar Polje (Muğla, Turkey), Bedri Kurtuluş, Çağdaş Sağir, Özgür Avşar
Assessment Of Metal-Metalloid Content Using Geostatistical Methods In Groundwater Of Karabağlar Polje (Muğla, Turkey), Bedri Kurtuluş, Çağdaş Sağir, Özgür Avşar
Bulletin of the Mineral Research and Exploration
In this research, heavy metals (Ti, Cr, Mn, Fe, Co, Ni, Cu, Zn, Mo, Cd, Ba, Pb) and metalloids (As) which were sampled from 84 wells used as drinking water and irrigation water resources in Karabaglar Karstic Polje (Mugla, Turkey) were analyzed. The results were evaluated by different statistical methods in order to investigate the interaction between elements. Ti, Mn, Fe, Zn, Mo and Pb were detected in many wells. According to the results, As and Cu has the strongest correlation (R=0.832). As-Ni (R=0.789) and Cu-Ni (R=0.776) are the other strong correlations. The relationship between these elements were also shown …
The Hydrogeologic Information In Cross-Borehole Complex Conductivity Data From An Unconsolidated Conglomeratic Sedimentary Aquifer, Andrew Binley, John Keery, Lee Slater, Warren Barrash, Mike Cardiff
The Hydrogeologic Information In Cross-Borehole Complex Conductivity Data From An Unconsolidated Conglomeratic Sedimentary Aquifer, Andrew Binley, John Keery, Lee Slater, Warren Barrash, Mike Cardiff
Geosciences Faculty Publications and Presentations
Accurate estimation of the hydrological properties of near-surface aquifers is important because these properties strongly influence groundwater flow and solute transport. Laboratory-based investigations have indicated that induced polarization (IP) properties of porous media may be linked, through either semi-empirical or fully mechanistic models, to hydrological properties including hydraulic conductivity. Therefore, there is a need for field assessments of the value of IP measurements in providing insights into the hydrological properties of aquifers. A cross-borehole IP survey was carried out at the Boise Hydrogeophysical Research Site (BHRS), an unconsolidated fluvial aquifer that has previously been well-studied with a variety of geophysical …
Deep Groundwater And Potential Subsurface Habitats Beneath An Antarctic Dry Valley, J. A. Mikucki, E. Auken, S. Tulaczyk, R. A. Virginia, C. Schamper, K. I. Sørensen, P. T. Doran, H. Dugan, N Foley
Deep Groundwater And Potential Subsurface Habitats Beneath An Antarctic Dry Valley, J. A. Mikucki, E. Auken, S. Tulaczyk, R. A. Virginia, C. Schamper, K. I. Sørensen, P. T. Doran, H. Dugan, N Foley
Dartmouth Scholarship
The occurrence of groundwater in Antarctica, particularly in the ice-free regions and along the coastal margins is poorly understood. Here we use an airborne transient electromagnetic (AEM) sensor to produce extensive imagery of resistivity beneath Taylor Valley. Regional- scale zones of low subsurface resistivity were detected that are inconsistent with the high resistivity of glacier ice or dry permafrost in this region. We interpret these results as an indication that liquid, with sufficiently high solute content, exists at temperatures well below freezing and considered within the range suitable for microbial life. These inferred brines are widespread within permafrost and extend …
Hydrogeophysical Characterization Of Anisotropy In The Biscayne Aquifer Using Geophysical Methods, Albert Yeboah-Forson
Hydrogeophysical Characterization Of Anisotropy In The Biscayne Aquifer Using Geophysical Methods, Albert Yeboah-Forson
FIU Electronic Theses and Dissertations
The anisotropy of the Biscayne Aquifer which serves as the source of potable water for Miami-Dade County was investigated by applying geophysical methods. Electrical resistivity imaging, self potential and ground penetration radar techniques were employed in both regional and site specific studies. In the regional study, electrical anisotropy and resistivity variation with depth were investigated with azimuthal square array measurements at 13 sites. The observed coefficient of electrical anisotropy ranged from 1.01 to 1.36. The general direction of measured anisotropy is uniform for most sites and trends W-E or SE-NW irrespective of depth. Measured electrical properties were used to estimate …
Quantifying The Relationship Among Ground Penetrating Radar Reflection Amplitudes, Horizontal Sub-Wavelength Bedrock Fracture Geometries, And Fluid Conductivities, Carolyn Morgan Tewksbury-Christle
Quantifying The Relationship Among Ground Penetrating Radar Reflection Amplitudes, Horizontal Sub-Wavelength Bedrock Fracture Geometries, And Fluid Conductivities, Carolyn Morgan Tewksbury-Christle
Masters Theses
Accurate characterization of subsurface fractures is indispensible for contaminant transport and fresh water resource modeling because discharge is cubically related to the fracture aperture; thus, minor errors in aperture estimates may yield major errors in a modeled hydrologic response. Ground penetrating radar (GPR) has been successfully used to noninvasively estimate fracture aperture for sub-horizontal fractures at outcrop scale, but limits on vertical and horizontal resolution are a concern. Theoretical formulations and field tests have demonstrated increased GPR amplitude response with the addition of a saline tracer in a sub-millimeter fracture; however, robust verification of existing theoretical equations without an accurate …
Hammer Seismic Reflection Imaging In An Urban Environment, Lee M. Liberty
Hammer Seismic Reflection Imaging In An Urban Environment, Lee M. Liberty
CGISS Publications and Presentations
Subsurface characterization within urban centers is critically important for city planners, municipalities, and engineers to estimate groundwater resources, track contaminants, assess earthquake or landslide hazards, and many other similar objectives. Improving geophysical imaging methods and results, while minimizing costs, provides greater opportunities for city/project planners and geophysicists alike to take advantage of the improved characterization afforded by the particular method. Seismic reflection results can provide hydrogeologic constraints for groundwater models, provide slip rate estimates for active faults, or simply map stratigraphy to provide target depth estimate. While many traditional urban seismic transects have included the use of vibroseis sources to …
Ground-Penetrating-Radar Reflection Attenuation Tomography With An Adaptive Mesh, Emily A. Hinz, John H. Bradford
Ground-Penetrating-Radar Reflection Attenuation Tomography With An Adaptive Mesh, Emily A. Hinz, John H. Bradford
CGISS Publications and Presentations
Ground-penetrating radar (GPR) attenuation-difference analysis can be a useful tool for studying fluid transport in the subsurface. Surface-based reflection attenuation-difference tomography poses a number of challenges that are not faced by crosshole attenuation surveys. We create and analyze a synthetic attenuation-difference GPR data set to determine methods for processing amplitude changes and inverting for conductivity differences from reflection data sets. Instead of using a traditional grid-based inversion, we use a data-driven adaptive-meshing algorithm to alter the model space and to create amore even distribution of resolution. Adaptive meshing provides a method for improving the resolution of the model space while …
Capacitive Conductivity Logging And Electrical Stratigraphy In A High-Resistivity Aquifer, Boise Hydrogeophysical Research Site, C. Jonathan Mwenifumbo, Warren Barrash, Michael D. Knoll
Capacitive Conductivity Logging And Electrical Stratigraphy In A High-Resistivity Aquifer, Boise Hydrogeophysical Research Site, C. Jonathan Mwenifumbo, Warren Barrash, Michael D. Knoll
CGISS Publications and Presentations
We tested a prototype capacitive-conductivity borehole tool in a shallow, unconfined aquifer with coarse, unconsolidated sediments and very-low-conductivity water at the Boise Hydrogeophysical Research Site (BHRS). Examining such a high-resistivity system provides a good test for the capacitive- conductivity tool because the conventional induction- conductivity tool (known to have limited effectiveness in high-resistivity systems) did not generate expressive well logs at the BHRS. The capacitive-conductivity tool demonstrated highly repeatable, low-noise behavior but poor correlation with the induction tool in the lower-conductivity portions of the stratigraphy where the induction tool was relatively unresponsive. Singular spectrum analysis of capacitive- conductivity logs reveals …
A Field Comparison Of Fresnel Zone And Ray-Based Gpr Attenuation-Difference Tomography For Time-Lapse Imaging Of Electrically Anomalous Tracer Or Contaminant Plumes, Timothy C. Johnson, Partha S. Routh, Warren Barrash, Michael D. Knoll
A Field Comparison Of Fresnel Zone And Ray-Based Gpr Attenuation-Difference Tomography For Time-Lapse Imaging Of Electrically Anomalous Tracer Or Contaminant Plumes, Timothy C. Johnson, Partha S. Routh, Warren Barrash, Michael D. Knoll
CGISS Publications and Presentations
Ground-penetrating radar (GPR) attenuation-difference tomography is a useful tool for imaging the migration of electrically anomalous tracer or contaminant plumes. Attenuation-difference tomography uses the difference in the trace amplitudes of tomographic data sets collected at different times to image the distribution of bulk-conductivity changes within the medium. The most common approach for computing the tomographic sensitivities uses ray theory, which is well understood and leads to efficient computations. However, ray theory requires the assumption that waves propagate at infinite frequency, and thus sensitivities are distributed along a line between the source and receiver. The infinite-frequency assumption in ray theory leads …
Ground-Penetrating Radar Theory And Application Of Thin-Bed Offset-Dependent Reflectivity, John H. Bradford, Jacob C. Deeds
Ground-Penetrating Radar Theory And Application Of Thin-Bed Offset-Dependent Reflectivity, John H. Bradford, Jacob C. Deeds
CGISS Publications and Presentations
Offset-dependent reflectivity or amplitude-variationwith- offset (AVO) analysis of ground-penetrating radar (GPR) data may improve the resolution of subsurface dielectric permittivity estimates. A horizontally stratified medium has a limiting layer thickness below which thin-bed AVO analysis is necessary. For a typical GPR signal, this limit is approximately 0.75 of the characteristic wavelength of the signal. Our approach to modeling the GPR thin-bed response is a broadband, frequency-dependent computation that utilizes an analytical solution to the three-interface reflectivity and is easy to implement for either transverse electric (TE) or transverse magnetic (TM) polarizations. The AVO curves for TE and TM modes differ …
Reflectivity Modeling Of A Ground-Penetrating-Radar Profile Of A Saturated Fluvial Formation, William P. Clement, Warren Barrash, Michael D. Knoll
Reflectivity Modeling Of A Ground-Penetrating-Radar Profile Of A Saturated Fluvial Formation, William P. Clement, Warren Barrash, Michael D. Knoll
Geosciences Faculty Publications and Presentations
Major horizons in radar reflection profiles may correlate with contacts between stratigraphic units or with structural breaks such as fault surfaces. Minor reflections may be caused by clutter or, in some cases, may indicate material properties or structure within stratigraphic units. In this study, we examine the physical basis for major and minor reflections observed in a shallow, unconfined, fluvial aquifer near Boise, Idaho, U. S. A. We compare a 2D profile from a surface ground-penetrating-radar reflection transect with the 1D modeled reflection profiles at three wells adjacent to the surface-reflection profile. The 1D models are based on dielectric constant …
Investigating The Stratigraphy Of An Alluvial Aquifer Using Crosswell Seismic Traveltime Tomography, Geoff J.M. Moret, Michael D. Knoll, Warren Barrash, William P. Clement
Investigating The Stratigraphy Of An Alluvial Aquifer Using Crosswell Seismic Traveltime Tomography, Geoff J.M. Moret, Michael D. Knoll, Warren Barrash, William P. Clement
CGISS Publications and Presentations
In this study, we investigate the use of crosswell P-wave seismic tomography to obtain spatially extensive information about subsurface sedimentary architecture and heterogeneity in alluvial aquifers. Our field site was a research wellfield in an unconfined aquifer near Boise, Idaho. The aquifer consists of a ~ 20-m-thick sequence of alluvial cobble- and-sand deposits, which have been subdivided into five stratigraphic units based on neutron porosity logs, grainsize analysis, and radar reflection data. We collected crosswell and borehole-to-surface seismic data in wells 17.1 m apart. We carefully considered the impact of well deviation, data quality control, and the choice of inversion …
Traveltime Inversion Of Vertical Radar Profiles, William P. Clement, Michael D. Knoll
Traveltime Inversion Of Vertical Radar Profiles, William P. Clement, Michael D. Knoll
Geosciences Faculty Publications and Presentations
Traveltimes of direct arrivals in vertical radar profiles (VRPs) are tomographically inverted to estimate the earth’s electromagnetic (EM) velocity between a surface transmitter and a downhole receiver. We determine the 1D interval velocity model that best fits the first-arrival traveltimes by using a weighted, damped, least-squares inversion scheme. We assess the accuracy of the velocity model using synthetic traveltimes from a known velocity-distribution model simulating an unconfined aquifer. The inverted velocity profile closely matched the velocity profile of the input model in the synthetic examples. Using vertical radar profile data from an unconfined aquifer near Boise, Idaho, we inverted traveltimes …
Potential Contaminants At A Dredged Spoil Placement Site, Charles City County, Virginia, As Revealed By Sequential Extraction, Jianwu Tang, G. Richard Whittecar, Karen H. Johannesson, W. Lee Daniels
Potential Contaminants At A Dredged Spoil Placement Site, Charles City County, Virginia, As Revealed By Sequential Extraction, Jianwu Tang, G. Richard Whittecar, Karen H. Johannesson, W. Lee Daniels
OES Faculty Publications
Backfills of dredged sediments onto a former sand and gravel mine site in Charles City County, VA may have the potential to contaminate local groundwater. To evaluate the mobility of trace elements and to identify the potential contaminants from the dredged sediments, a sequential extraction scheme was used to partition trace elements associated with the sediments from the local aquifer and the dredged sediments into five fractions: exchangeable, acidic, reducible, oxidizable, and residual phases. Sequential extractions indicate that, for most of the trace elements examined, the residual phases account for the largest proportion of the total concentrations, and their total …
Depth Characterization Of Shallow Aquifers With Seismic Reflection, Part Ii—Prestack Depth Migration And Field Examples, John H. Bradford, D. S. Sawyer
Depth Characterization Of Shallow Aquifers With Seismic Reflection, Part Ii—Prestack Depth Migration And Field Examples, John H. Bradford, D. S. Sawyer
CGISS Publications and Presentations
It is common in shallow seismic studies for the compressional-wave velocity in unconsolidated sediments to increase by a factor of four or more at the transition from dry or partial water saturation to full saturation. Under these conditions, conventional NMO velocity analysis fails and leads to large depth and layer thickness estimates if the Dix equation is assumed valid. Prestack depth migration (PSDM) is a means of improving image accuracy. A comparison of PSDM with conventional NMO processing for three field examples from differing hydrogeologic environments illustrates that PSDM can significantly improve image quality and accuracy.
Depth Characterization Of Shallow Aquifers With Seismic Reflection, Part I—The Failure Of Nmo Velocity Analysis And Quantitative Error Prediction, John H. Bradford
Depth Characterization Of Shallow Aquifers With Seismic Reflection, Part I—The Failure Of Nmo Velocity Analysis And Quantitative Error Prediction, John H. Bradford
CGISS Publications and Presentations
As seismic reflection data become more prevalent as input for quantitative environmental and engineering studies, there is a growing need to assess and improve the accuracy of reflection processing methodologies. It is common for compressional-wave velocities to increase by a factor of four or more where shallow, unconsolidated sediments change from a dry or partially watersaturated regime to full saturation. While this degree of velocity contrast is rare in conventional seismology, it is a common scenario in shallow environments and leads to significant problems when trying to record and interpret reflections within about the first 30 m below the water …
An Assessment Of Airborne Electromagnetics For Hydrogeological Interpretation In The Wheatbelt, Western Australia, Peter De Broekert
An Assessment Of Airborne Electromagnetics For Hydrogeological Interpretation In The Wheatbelt, Western Australia, Peter De Broekert
Resource management technical reports
No abstract provided.