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Articles 421 - 450 of 524
Full-Text Articles in Geophysics and Seismology
Estimating The Rayleigh-Wave Impulse Response Between Seismic Stations With The Cross Terms Of The Green Tensor, Kasper Van Wijk, T. Dylan Mikesell, Vera Schulte-Pelkum, Josh Stachnik
Estimating The Rayleigh-Wave Impulse Response Between Seismic Stations With The Cross Terms Of The Green Tensor, Kasper Van Wijk, T. Dylan Mikesell, Vera Schulte-Pelkum, Josh Stachnik
CGISS Publications and Presentations
The development of ambient noise tomography has provided a powerful tool to investigate the Earth's subsurface with increased resolution. Most commonly, surface-wave tomography is performed on inter-station estimates of the vertical component of Rayleigh waves, stemming from crosscorrelations of ocean-generated noise. Here, we estimate the cross terms of the Rayleigh-wave Green tensor, and show this is less sensitive to signal not in-line with the seismic stations. We illustrate this result with the Batholiths temporary seismic deployment, showing estimates of the Rayleigh wave with a higher signal-to-noise ratio and a consequently better phase-velocity dispersion curve. This approach provides an opportunity for …
Establishing Confidence In Surface Wave Determined Soil Profiles, Paul Michaels
Establishing Confidence In Surface Wave Determined Soil Profiles, Paul Michaels
CGISS Publications and Presentations
Surface waves can be used to determine the shear velocity profile from the ground surface to some depth limited by the spectral band of the seismic source. A number of factors influence the uncertainties of the determined profile. The field acquisition factors include the deployment geometry of geophones, the spectral characteristics of the geophones, recording instruments, and seismic source. A key data processing factor is the determination of a dispersion curve from the field recordings. Finally, there are important choices in conducting the inversion of the dispersion curve which leads to the final soil profile. Even if the field factors …
Interpretation Of Rayleigh-Wave Ellipticity Observed With Multicomponent Passive Seismic Interferometry At Hekla Volcano, Iceland, Matthew M. Haney, Andrew Nies, Tim Masterlark, Sarah Needy, Rikke Pedersen
Interpretation Of Rayleigh-Wave Ellipticity Observed With Multicomponent Passive Seismic Interferometry At Hekla Volcano, Iceland, Matthew M. Haney, Andrew Nies, Tim Masterlark, Sarah Needy, Rikke Pedersen
CGISS Publications and Presentations
The 2010 eruption of Eyjafjallajökull has drawn increased attention to Iceland’s Eastern Volcanic Zone (EVZ) due to the threat it poses to the heavily used air-traffic corridors of the northern Atlantic Ocean. Within the EVZ, Hekla is historically one of the most active volcanoes and has exhibited a decadal eruption pattern for the past 40 years. Hekla most recently erupted in 2000 and is thus ripe for another decadal eruption. Because Hekla is generally aseismic, except for a brief time period (hours) leading up to an eruption, monitoring has previously depended on precursory deformation signals (Linde et al., 1993). As …
Taxonomy, Nomenclature, And Evolution Of The Early Schubertellid Fusulinids, Vladimir I. Davydov
Taxonomy, Nomenclature, And Evolution Of The Early Schubertellid Fusulinids, Vladimir I. Davydov
Geosciences Faculty Publications and Presentations
The types of the species belonging to the fusulinid genera Schubertella and Eoschubertella were examined from publications and type collections. Eoschubertella in general possesses all the features of Schubertella and therefore is a junior synonym of the latter. However, the concept of Eoschubertella best describes the genus Schubertina with its type species Schubertina curculi. Schubertina is closely related to the newly established genus Grovesella the concept of which is emended in this paper. Besides Schubertella, Schubertina, and Grovesella, the genera Mesoschubertella, Biwaella are reviewed and three new species, Grovesella nevadensis, Biwaella zhikalyaki, and Biwaella poletaevi, are described. The phylogenetic relationships …
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 …
Late Holocene Relationships Among Fire, Climate, And Vegetation In Rangeland Ecosystems Of Southwestern Idaho, Nathan A. Nelson, Jennifer Pierce
Late Holocene Relationships Among Fire, Climate, And Vegetation In Rangeland Ecosystems Of Southwestern Idaho, Nathan A. Nelson, Jennifer Pierce
Geosciences Faculty Publications and Presentations
Rangelands are characterized by more arid climates than forested regions; therefore, establishing fire histories using traditional methods (e.g. fire-scars from trees or charcoal in lake sediments) is problematic. This study uses radiocarbon dating of charcoal preserved in alluvial fans and stream deposits to reconstruct a record of fire and geomorphic response in rangelands of southwestern Idaho. Samples indicate three primary periods of fire-related activity: 4400 – 4000, 2000 – 1400, and 650-400 cal yr BP. Charcoal macrofossil identification and comparison with other regional climate and fire records indicate this area has likely switched between a "fuel-limited" system (fires limited by …
Stable Isotopes Of Fossil Teeth Corroborate Key General Circulation Model Predictions For The Last Glacial Maximum In North America, Matthew J. Kohn, Moriah Mckay
Stable Isotopes Of Fossil Teeth Corroborate Key General Circulation Model Predictions For The Last Glacial Maximum In North America, Matthew J. Kohn, Moriah Mckay
Geosciences Faculty Publications and Presentations
Oxygen isotope data provide a key test of general circulation models (GCMs) for the Last Glacial Maximum (LGM) in North America, which have otherwise proved difficult to validate. High δ18O pedogenic carbonates in central Wyoming have been interpreted to indicate increased summer precipitation sourced from the Gulf of Mexico. Here we show that tooth enamel δ18O of large mammals, which is strongly correlated with local water and precipitation δ18O, is lower during the LGM in Wyoming, not higher. Similar data from Texas, California, Florida and Arizona indicate higher δ18O values than in the Holocene, which is also predicted by GCMs. …
Carbon Isotope Compositions Of Terrestrial C3 Plants As Indicators Of (Paleo)Ecology And (Paleo)Climate, Matthew J. Kohn
Carbon Isotope Compositions Of Terrestrial C3 Plants As Indicators Of (Paleo)Ecology And (Paleo)Climate, Matthew J. Kohn
Geosciences Faculty Publications and Presentations
A broad compilation of modern carbon isotope compositions in all C3 plant types shows a monotonic increase in δ13C with decreasing mean annual precipitation (MAP) that differs from previous models. Corrections for temperature, altitude, or latitude are smaller than previously estimated. As corrected for altitude, latitude, and the δ13C of atmospheric CO2, these data permit refined interpretation of MAP, paleodiet, and paleoecology of ecosystems dominated by C3 plants, either prior to 7–8 million years ago (Ma), or more recently at mid- to high latitudes. Twenty-nine published paleontological studies suggest preservational or scientific bias toward …
Rare Earth And High Field Strength Element Partitioning Between Iron-Rich Clinopyroxenes And Felsic Liquids, Paul H. Olin, John A. Wolff
Rare Earth And High Field Strength Element Partitioning Between Iron-Rich Clinopyroxenes And Felsic Liquids, Paul H. Olin, John A. Wolff
Geosciences Faculty Publications and Presentations
Rare earth elements are commonly assumed to substitute only for Ca in clinopyroxene because of the similarity of ionic radii for REE3+ and Ca2+ in 8-fold coordination. The assumption is valid for Mg-rich clinopyroxenes for which observed mineral/melt partition coefficients are readily predicted by the lattice strain model for substitution onto a single site (e.g. Wood and Blundy, 1997). We show that natural Fe-rich pyroxenes in both silica-undersaturated and -oversaturated magmatic systems deviate from this behavior. Salites (Mg# 48 to 59) in phonolites from Tenerife, ferrohedenbergites (Mg# 14.2 to 16.2) from the rhyolitic Bandelier Tuff, and ferroaugites (Mg# …
Autonomous Fmcw Radar Survey Of Antarctic Shear Zone, Gary Koh, James H. Lever, Steven A. Arcone, Hans-Peter Marshall, Laura E. Ray
Autonomous Fmcw Radar Survey Of Antarctic Shear Zone, Gary Koh, James H. Lever, Steven A. Arcone, Hans-Peter Marshall, Laura E. Ray
CGISS Publications and Presentations
Radar survey of the Antarctic shear zone was conducted using an ultra-wideband (2-10 GHz) frequency modulated continuous wave (FMCW) radar. The radar was mounted on a sled and pulled by a robot that was specifically designed to operate in a harsh polar environment. Our FMCW radar had good penetration through Antarctic snow and we observed snow stratigraphy to a depth of 20 m. The radar images also revealed multiple crevasses in the shear zone. Our results demonstrate that autonomous survey using high frequency radar is feasible and safe approach for detecting hidden crevasses.
2d Ground-Penetrating Radar Avo Response To A 3d Dielectric Permittivity Anomaly, John H. Bradford
2d Ground-Penetrating Radar Avo Response To A 3d Dielectric Permittivity Anomaly, John H. Bradford
CGISS Publications and Presentations
To evaluate the amplitude vs offset response of GPR to small distributions of hydrocarbon contamination, I acquired multi-offset 450 MHz GPR data in TE and TM modes over a buried rectangular tank filled with gasoline saturated sand. All dimensions of the tank were less than one wavelength at the characteristic antenna frequency. The permittivity ratio at the moist sand/gasoline sand boundary, estimated by fitting the Fresnel equations to the observed amplitudes and by Brewster's Angle analysis, differed from that obtained through migration velocity analysis by no more than 12%. 2D FDTD modeling reproduced amplitude characteristics for 3 o f 4 …
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 …
Arctic Landscapes In Transition: Responses To Thawing Permafrost, James P. Mcnamara
Arctic Landscapes In Transition: Responses To Thawing Permafrost, James P. Mcnamara
Geosciences Faculty Publications and Presentations
Observations indicate that over the past several decades, geomorphic processes in the Arctic have been changing or intensifying. Coastal erosion, which currently supplies most of the sediment and carbon to the Arctic Ocean [Rachold et al., 2000], may have doubled since 1955 [Mars and Houseknecht, 2007]. Further inland, expansion of channel networks [Toniolo et al., 2009] and increased river bank erosion [Costard et al., 2007] have been attributed to warming. Lakes, ponds, and wetlands appear to be more dynamic, growing in some areas, shrinking in others, and changing distribution across lowland regions …
Characterization Of Englacial Voids Using Radar Velocity Anisotropy, Joshua D. Nichols
Characterization Of Englacial Voids Using Radar Velocity Anisotropy, Joshua D. Nichols
Boise State University Theses and Dissertations
Glacial hydrology plays an important role in the motion and melt of glaciers. The transport of water through glacial ice is still poorly understood. Previous studies show that much of the water is stored and routed through planar voids within the glacier. From borehole observations and previous radar surveys, the voids appear to have a preferential orientation. Transverse waves, including radar waves, and shear seismic waves, travel at different velocities when polarized at different orientations relative to aligned inclusions. I conducted two georadar surveys on Bench glacier, in the Chugach Mountains, AK. Bench glacier has been the field site of …
Reproducibility Of Soil Moisture Ensembles When Representing Soil Parameter Uncertainty Using A Latin Hypercube-Based Approach With Correlation Control, Alejandro N. Flores, Dara Entekhabi, Rafael L. Bras
Reproducibility Of Soil Moisture Ensembles When Representing Soil Parameter Uncertainty Using A Latin Hypercube-Based Approach With Correlation Control, Alejandro N. Flores, Dara Entekhabi, Rafael L. Bras
Geosciences Faculty Publications and Presentations
Representation of model input uncertainty is critical in ensemble‐based data assimilation. Monte Carlo sampling of model inputs produces uncertainty in the hydrologic state through the model dynamics. Small Monte Carlo ensemble sizes are desirable because of model complexity and dimensionality but potentially lead to sampling errors and correspondingly poor representation of probabilistic structure of the hydrologic state. We compare two techniques to sample soil hydraulic and thermal properties (SHTPs): (1) Latin Hypercube (LH) based sampling with correlation control and (2) random sampling from SHTP marginal distributions. A hydrology model is used to project SHTP uncertainty onto the soil moisture state …
Seismicity Associated With Geothermal Systems, Randi Walters
Seismicity Associated With Geothermal Systems, Randi Walters
McNair Scholars Research Journal
Studying natural and induced seismicity associated with geothermal systems can provide information regarding the location and magnitude of hydraulic fracturing. Understanding the fracture system can aid geothermal exploration. In addition, seismicity can affect the output of a geothermal reservoir, and potentially be a seismic hazard to the surrounding area. This study focuses on two geothermal systems: the Raft River Geothermal System (RRGS) in southern Idaho and the Mt. Princeton Geothermal System (MPGS) in central Colorado. The seismic data analyzed for the RRGS is from the broadband sensors that are part of the EarthScope Project’s Transportable Array (TA), while the seismic …
Assessing The Potential To Detect Oil Spills In And Under Snow Using Airborne Ground-Penetrating Radar, John H. Bradford, David F. Dickens, Per Johan Brandvik
Assessing The Potential To Detect Oil Spills In And Under Snow Using Airborne Ground-Penetrating Radar, John H. Bradford, David F. Dickens, Per Johan Brandvik
CGISS Publications and Presentations
With recent increased interest in oil and gas exploration and development in the Arctic comes increased potential for an accidental hydrocarbon release into the cryosphere, including within and at the base of snow. There is a critical need to develop effective and reliable methods for detecting such spills. Numerical modeling shows that ground-penetrating radar (GPR) is sensitive to the presence of oil in the snow pack over a broad range of snow densities and oil types. Oil spills from the surface drain through the snow by the mechanisms of unsaturated flow and form geometrically complex distributions that are controlled by …
High-Precision U-Pb Zircon Age Calibration Of The Global Carboniferous Time Scale And Milankovitch Band Cyclicity In The Donets Basin, Eastern Ukraine, Vladimir I. Davydov, James L. Crowley, Mark D. Schmitz, Vladislav I. Poletaev
High-Precision U-Pb Zircon Age Calibration Of The Global Carboniferous Time Scale And Milankovitch Band Cyclicity In The Donets Basin, Eastern Ukraine, Vladimir I. Davydov, James L. Crowley, Mark D. Schmitz, Vladislav I. Poletaev
Geosciences Faculty Publications and Presentations
High-precision ID-TIMS U-Pb zircon ages for 12 interstratified tuffs and tonsteins are used to radiometrically calibrate the detailed lithostratigraphic, cyclostratigraphic, and biostratigraphic framework of the Carboniferous Donets Basin of eastern Europe. Chemical abrasion of zircons, use of the internationally calibrated EARTHTIME mixed U-Pb isotope dilution tracer, and improved mass spectrometry guided by detailed error analysis have resulted in an age resolution of
Accurate Inversion Of High-Resolution Snow Penetrometer Signals For Microstructural And Micromechanical Properties, Hans-Peter Marshall, Jerome B. Johnson
Accurate Inversion Of High-Resolution Snow Penetrometer Signals For Microstructural And Micromechanical Properties, Hans-Peter Marshall, Jerome B. Johnson
CGISS Publications and Presentations
Measurements of snow using a high-resolution micropenetrometer can be used to discriminate between different snow types; in lower-density snow the signal is sensitive to microstructure, and micromechanical properties can be estimated. Although a physics-based snow penetration theory was first developed almost a decade ago, since that time the majority of studies using snow micropenetrometers have focused on using direct hardness measurements in statistical relationships. We use Monte-Carlo simulations to rigorously test the existing physics-based snow micropenetration theories over a wide range of parameters. These tests revealed four major sources of error in the inversion, which are corrected in this analysis. …
Modeling Soil Depth From Topographic And Land Cover Attributes, Teklu K. Tesfa, David G. Tarboton, David G. Chandler, James P. Mcnamara
Modeling Soil Depth From Topographic And Land Cover Attributes, Teklu K. Tesfa, David G. Tarboton, David G. Chandler, James P. Mcnamara
Geosciences Faculty Publications and Presentations
Soil depth is an important input parameter in hydrological and ecological modeling. Presently, the soil depth data available in national soil databases (STATSGO and SSURGO) from the Natural Resources Conservation Service are provided as averages within generalized land units (map units). Spatial uncertainty within these units limits their applicability for distributed modeling in complex terrain. This work reports statistical models for prediction of soil depth in a semiarid mountainous watershed that are based upon the relationship between soil depth and topographic and land cover attributes. Soil depth was surveyed by driving a rod into the ground until refusal at locations …
Infrasonic Ambient Noise Interferometry From Correlations Of Microbaroms, Matthew M. Haney
Infrasonic Ambient Noise Interferometry From Correlations Of Microbaroms, Matthew M. Haney
CGISS Publications and Presentations
We show that microbaroms, continuous infrasound fluctuations resulting from the interaction of the ocean with the atmosphere, have long-range correlation properties that make it possible to estimate the impulse response between two microphones from passive recordings. The processing is analogous to methods employed in the emerging field of ambient noise seismology, where the random noise source is the ocean coupling with the solid Earth (microseisms) instead of the atmosphere (microbaroms). We find that timedependent temperature fields and temperature inversions determine the character of infrasonic impulse responses at Fourpeaked Volcano in Alaska. Applications include imaging and monitoring the gross structure of …
Estimating Debye Parameters From Gpr Reflection Data Using Spectral Ratios, John H. Bradford
Estimating Debye Parameters From Gpr Reflection Data Using Spectral Ratios, John H. Bradford
Geosciences Faculty Publications and Presentations
In the GPR frequency range, electromagnetic wave attenuation is largely controlled by dielectric relaxation processes. A primary relaxation commonly occurs in the 10 – 100 MHz range for many earth materials in which the GPR signal propagates effectively. This relaxation leads to strong nonlinearity in the frequency dependent attenuation and occurs in a frequency range that is often used for groundwater investigations. This non-linearity complicates data analysis but also may provide additional material property information. I investigate inversion for Debye relaxation parameters directly from GPR reflection data, including increasing the bandwidth of the signal by summing the response from 25 …
Improved Confidence In (U-Th)/He Thermochronology Using The Laser Microprobe: An Example From A Pleistocene Leucogranite, Nanga Parbat, Pakistan, J. W. Boyce, K. V. Hodges, D. King, James L. Crowley, M. Jercinovic, N. Chatterjee, S. A. Bowring, M. Searle
Improved Confidence In (U-Th)/He Thermochronology Using The Laser Microprobe: An Example From A Pleistocene Leucogranite, Nanga Parbat, Pakistan, J. W. Boyce, K. V. Hodges, D. King, James L. Crowley, M. Jercinovic, N. Chatterjee, S. A. Bowring, M. Searle
Geosciences Faculty Publications and Presentations
The newly developed laser microprobe (U-Th)/He thermochronometer permits, for the first time, the ability to generate precise (U-Th)/He cooling ages for even very young (Ma) samples with a spatial resolution on the order of tens of micrometers. This makes it possible to test the reproducibility of independent (U-Th)/He age determinations within individual crystals, further increasing the reliability of the method. As an example, we apply it here to a Pleistocene granite from Nanga Parbat, Pakistan, where previous constraints on the thermal history are consistent with rapid exhumation and cooling. Twenty-one (U-Th)/He dates determined on two monazite crystals from a single …
Obtaining Parsimonious Hydraulic Conductivity Fields Using Head And Transport Observations: A Bayesian Geostatistical Parameter Estimation Approach, Michael Fienen, R. Hunt, D. Krabbenhoft, Tom Clemo
Obtaining Parsimonious Hydraulic Conductivity Fields Using Head And Transport Observations: A Bayesian Geostatistical Parameter Estimation Approach, Michael Fienen, R. Hunt, D. Krabbenhoft, Tom Clemo
CGISS Publications and Presentations
Flow path delineation is a valuable tool for interpreting the subsurface hydrogeochemical environment. Different types of data, such as groundwater flow and transport, inform different aspects of hydrogeologic parameter values (hydraulic conductivity in this case) which, in turn, determine flow paths. This work combines flow and transport information to estimate a unified set of hydrogeologic parameters using the Bayesian geostatistical inverse approach. Parameter flexibility is allowed by using a highly parameterized approach with the level of complexity informed by the data. Despite the effort to adhere to the ideal of minimal a priori structure imposed on the problem, extreme contrasts …
Complex Dielectric Permittivity Measurements From Ground-Penetrating Radar Data To Estimate Snow Liquid Water Content In The Pendular Regime, John H. Bradford, Joel T. Harper, Joel Brown
Complex Dielectric Permittivity Measurements From Ground-Penetrating Radar Data To Estimate Snow Liquid Water Content In The Pendular Regime, John H. Bradford, Joel T. Harper, Joel Brown
CGISS Publications and Presentations
Monitoring the snow water equivalent (SWE) is critical to effective management of water resources in many parts of the world that depend on the mountain snowpack for water storage. There are currently no methods to remotely sense SWE with accuracy over large lateral distances in the steep and often forested terrain of mountain basins. Previous studies have shown that measurements of ground-penetrating radar (GPR) velocity can provide accurate estimates of SWE in dry snow. Introduction of liquid water into the snowpack results in a three-phase system that cannot be accurately characterized with GPR velocity alone. We show that measuring the …
Seismic Wave Attenuation In Carbonates, Ludmila Adam, M. Batzle, K. T. Lewallen, Kasper Van Wijk
Seismic Wave Attenuation In Carbonates, Ludmila Adam, M. Batzle, K. T. Lewallen, Kasper Van Wijk
CGISS Publications and Presentations
The effect of pore fluids on seismic wave attenuation in carbonate rocks is important for interpreting remote sensing observations of carbonate reservoirs undergoing enhanced oil recovery. Here we measure the elastic moduli and attenuation in the laboratory for five carbonate samples with 20% to 30% porosity and permeability between 0.03 and 58.1 mdarcy. Contrary to most observations in sandstones, bulk compressibility losses dominate over shear wave losses for dry samples and samples fully saturated with either liquid butane or brine. This observation holds for four out of five samples at seismic (10–1000 Hz) and ultrasonic frequencies (0.8 MHz) and reservoir …
Observation And Modeling Of Source Effects In Coda Wave Interferometry At Pavlof Volcano, Matthew M. Haney, Kasper Van Wijk, Leiph A. Preston, David F. Aldridge
Observation And Modeling Of Source Effects In Coda Wave Interferometry At Pavlof Volcano, Matthew M. Haney, Kasper Van Wijk, Leiph A. Preston, David F. Aldridge
CGISS Publications and Presentations
We examine seismic records of repeating explosions from Pavlof volcano, Alaska, during its 2007 eruption. Repetitive explosions are typical of Strombolian-style eruptions and allow measurement of relative time shifts between similar late-arriving phases using the technique called coda wave interferometry (Snieder et al., 2002). The measurements enable the detection of small changes in the volcanic interior of Pavlof. We are able to resolve an increase in the relative traveltime change of late-arriving seismic waves on the order of 0.3% over the course of two weeks. Based on the spectra of the explosions, their location inside the magma conduit, previous studies …
Numerical Modeling Of Time-Lapse Seismic Experiments To Monitor Co2 Sequestration In A Layered Basalt Reservoir, Murari Khatiwada
Numerical Modeling Of Time-Lapse Seismic Experiments To Monitor Co2 Sequestration In A Layered Basalt Reservoir, Murari Khatiwada
Boise State University Theses and Dissertations
Instead of allowing carbon dioxide (CO2) generated from the burning of hydrocarbons to escape into the atmosphere, CO2 can be captured and stored. For the long term mitigation of the increasing amount of CO2 emissions, its sequestration in geological formations is promising. As a measure, its short and long term monitoring is equally important for environmental and health safety issues. The seismic method is proposed as a non-invasive monitoring technique for geological sequestration of CO2. Based on the positive results obtained from reservoir monitoring during enhanced oil recovery with CO2 floods, geoscientists plan …
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 …
The Virtual Refraction: Useful Spurious Energy In Seismic Interferometry, Dylan Mikesell, Kasper Van Wijk, Alexander Calvert, Matthew M. Haney
The Virtual Refraction: Useful Spurious Energy In Seismic Interferometry, Dylan Mikesell, Kasper Van Wijk, Alexander Calvert, Matthew M. Haney
CGISS Publications and Presentations
Seismic interferometry is rapidly becoming an established technique to recover the Green’s function between receivers, but practical limitations in the source-energy distribution inevitably lead to spurious energy in the results. Instead of attempting to suppress all such energy, we use a spurious wave associated with the crosscorrelation of refracted energy at both receivers to infer estimates of subsurface parameters. We named this spurious event the virtual refraction. Illustrated by a numerical two-layer example, we found that the slope of the virtual refraction defines the velocity of the faster medium and that the stationary-phase point in the correlation gather provides the …