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Articles 1 - 12 of 12
Full-Text Articles in Physical Sciences and Mathematics
A Ten-Year Record Of Supraglacial Lake Evolution And Rapid Drainage In West Greenland Using An Automated Processing Algorithm For Multispectral Imagery, B. F. Morriss, R. L. Hawley, J. W. Chipman, L. C. Andrews
A Ten-Year Record Of Supraglacial Lake Evolution And Rapid Drainage In West Greenland Using An Automated Processing Algorithm For Multispectral Imagery, B. F. Morriss, R. L. Hawley, J. W. Chipman, L. C. Andrews
Dartmouth Scholarship
The rapid drainage of supraglacial lakes introduces large pulses of meltwater to the subglacial environment and creates moulins, surface-to-bed conduits for future melt. Introduction of water to the subglacial system has been shown to affect ice flow, and modeling suggests that variability in water supply and delivery to the subsurface play an important role in the development of the subglacial hydrologic system and its ability to enhance or mitigate ice flow. We developed a fully automated method for tracking meltwater and rapid drainages in large (> 0.125 km2) perennial lakes and applied it to a 10 yr time …
Hydraulic Conductivity Imaging From 3-D Transient Hydraulic Tomography At Several Pumping/Observation Densities, Michael Cardiff, Warren Barrash, Peter K. Kitanidis
Hydraulic Conductivity Imaging From 3-D Transient Hydraulic Tomography At Several Pumping/Observation Densities, Michael Cardiff, Warren Barrash, Peter K. Kitanidis
CGISS Publications and Presentations
3-D Hydraulic tomography (3-D HT) is a method for aquifer characterization whereby the 3-D spatial distribution of aquifer flow parameters (primarily hydraulic conductivity, K) is estimated by joint inversion of head change data from multiple partially penetrating pumping tests. While performance of 3-D HT has been studied extensively in numerical experiments, few field studies have demonstrated the real-world performance of 3-D HT. Here we report on a 3-D transient hydraulic tomography (3-D THT) field experiment at the Boise Hydrogeophysical Research Site which is different from prior approaches in that it represents a “baseline” analysis of 3-D THT performance using …
Megathrust Splay Faults At The Focus Of The Prince William Sound Asperity, Alaska, Lee M. Liberty, Shaun P. Finn, Peter J. Haeussler, Thomas L. Pratt, Andrew Peterson
Megathrust Splay Faults At The Focus Of The Prince William Sound Asperity, Alaska, Lee M. Liberty, Shaun P. Finn, Peter J. Haeussler, Thomas L. Pratt, Andrew Peterson
CGISS Publications and Presentations
[1] High-resolution sparker and crustal-scale air gun seismic reflection data, coupled with repeat bathymetric surveys, document a region of repeated coseismic uplift on the portion of the Alaska subduction zone that ruptured in 1964. This area defines the western limit of Prince William Sound. Differencing of vintage and modern bathymetric surveys shows that the region of greatest uplift related to the 1964 Great Alaska earthquake was focused along a series of subparallel faults beneath Prince William Sound and the adjacent Gulf of Alaska shelf. Bathymetric differencing indicates that 12 m of coseismic uplift occurred along two faults that reached the …
Using Svd For Improved Interferometric Green's Function Retrieval, Gabriela Melo, Alison Malcolm, Dylan Mikesell, Kasper Van Wijk
Using Svd For Improved Interferometric Green's Function Retrieval, Gabriela Melo, Alison Malcolm, Dylan Mikesell, Kasper Van Wijk
CGISS Publications and Presentations
Seismic interferometry (SI) is a technique used to estimate the Green’s function (GF) between two receiver locations, as if there were a source at one of the receiver locations. However, in many applications, the requirements to recover the exact GF are not satisfied and SI yields a poor estimate of the GF. For these non-ideal cases, we improve the interferometric GFs, by applying singular value decomposition (SVD) to the cross-correlations before stacking. The SVD approach preserves energy that is stationary in the cross-correlations, which is the energy that contributes most to the GF recovery, and attenuates non-stationary energy, which leads …
Aquifer Heterogeneity Characterization With Oscillatory Pumping: Sensitivity Analysis And Imaging Potential, M. Cardiff, T. Bakhos, P. K. Kitanidis, W. Barrash
Aquifer Heterogeneity Characterization With Oscillatory Pumping: Sensitivity Analysis And Imaging Potential, M. Cardiff, T. Bakhos, P. K. Kitanidis, W. Barrash
CGISS Publications and Presentations
[1] Periodic pumping tests, in which a fluid is extracted during half a period, then reinjected, have been used historically to estimate effective aquifer properties. In this work, we suggest a modified approach to periodic pumping test analysis in which one uses several periodic pumping signals of different frequencies as stimulation, and responses are analyzed through inverse modeling using a “steady-periodic” model formulation. We refer to this strategy as multifrequency oscillatory hydraulic imaging. Oscillating pumping tests have several advantages that have been noted, including no net water extraction during testing and robust signal measurement through signal processing. Through numerical experiments, …
Changes In Elastic Wave Velocity And Rock Microstructure Due To Basalt-Co2-Water Reactions, Ludmila Adam, Kasper Van Wijk, Thomas Otheim, Michael Batzle
Changes In Elastic Wave Velocity And Rock Microstructure Due To Basalt-Co2-Water Reactions, Ludmila Adam, Kasper Van Wijk, Thomas Otheim, Michael Batzle
CGISS Publications and Presentations
The chemical interaction between carbon dioxide, water, and basalt is a common process in the earth, which results in the dissolution of primary minerals that later precipitate as alteration minerals. This occurs naturally in volcanic settings, but more recently basalts have been suggested as reservoirs for sequestration of anthropogenic CO2. In both the natural and man-made cases, rock-fluid reactions lead to the precipitation of carbonates. Here, we quantify changes in ultrasonic wave speeds, associated with changes in the frame of whole-rock basalts, as CO2 and basalt react. After 30weeks of reactions and carbonate precipitation, the ultrasonic wave …
The Need To Adapt The Exploration Model From The Oil Patch To Contaminated-Site Characterization: A Case From Hill Afb, Utah, Usa, John H. Bradford, Esther Babcock
The Need To Adapt The Exploration Model From The Oil Patch To Contaminated-Site Characterization: A Case From Hill Afb, Utah, Usa, John H. Bradford, Esther Babcock
CGISS Publications and Presentations
For decades, the oil industry has employed a working model for hydrocarbon exploration in which large-scale geophysical surveys are undertaken prior to a second phase of intensive, targeted drilling. This latter phase may be conducted in conjunction with further focused geophysical studies. The geophysical surveys provide lateral coverage and continuity that are used to drive placement of drilling locations. The reason for this approach is simple: wells are expensive relative to geophysical surveys. Also, practical limits on lateral coverage preclude optimization of exploration targets based on well information alone.
Noncontacting Benchtop Measurements Of The Elastic Properties Of Shales, Thomas E. Blum, Ludmila Adam, Kasper Van Wijk
Noncontacting Benchtop Measurements Of The Elastic Properties Of Shales, Thomas E. Blum, Ludmila Adam, Kasper Van Wijk
CGISS Publications and Presentations
We evaluated a laser-based noncontacting method to measure the elastic anisotropy of horizontal shale cores. Whereas conventional transducer data contained an ambiguity between phase and group velocity measurements, small laser source and receiver footprints on typical core samples ensured group velocity information in our laboratory measurements. With a single dense acquisition of group velocity versus group angle on a horizontal core, we estimated the elastic constants C11, C33, and C55 directly from ultrasonic waveforms, and C13 from a least-squares fit of modeled to measured group velocities. The observed significant P-wave velocity and attenuation anisotropy …
K-12 Geoscience Workshops And Freshman Field Camp: Txkorp Outreach [Abstract], Kevin W. Stafford, Melinda G. Shaw-Faulkner, Wesley A. Brown
K-12 Geoscience Workshops And Freshman Field Camp: Txkorp Outreach [Abstract], Kevin W. Stafford, Melinda G. Shaw-Faulkner, Wesley A. Brown
Faculty Presentations
No abstract provided.
Clustering Revisited: A Spectral Analysis Of Microseismic Events, Deborah Fagan, Kasper Van Wijk, James Rutledge
Clustering Revisited: A Spectral Analysis Of Microseismic Events, Deborah Fagan, Kasper Van Wijk, James Rutledge
CGISS Publications and Presentations
Identifying individual subsurface faults in a larger fault system is important to characterize and understand the relationship between microseismicity and subsurface processes. This information can potentially help drive reservoir management and mitigate the risks of natural or induced seismicity. We have evaluated a method of statistically clustering power spectra from microseismic events associated with an enhanced oil recovery operation in southeast Utah. Specifically, we were able to provide a clear distinction within a set of events originally designated in the time domain as a single cluster and to identify evidence of en echelon faulting. Subtle time-domain differences between events were …
Recognizing And Modeling Variable Drawdown Due To Evapotranspiration In A Semiarid Riparian Zone Considering Local Differences In Vegetation And Distance From A River Source, Brady Johnson, Bwalya Malama, Warren Barrash, Alejandro N. Flores
Recognizing And Modeling Variable Drawdown Due To Evapotranspiration In A Semiarid Riparian Zone Considering Local Differences In Vegetation And Distance From A River Source, Brady Johnson, Bwalya Malama, Warren Barrash, Alejandro N. Flores
CGISS Publications and Presentations
Riparian zones in semiarid regions often exhibit high rates of evapotranspiration (ET) in spite of low-soil moisture content due to the presence of phreatophytic vegetation that is able to withdraw water from shallow aquifers. This work seeks to better define the relationship between ET, the saturated zone and the river boundary by comparing observed water table drawdown records to analytically modeled drawdown in fully penetrating wells of an unconfined aquifer in response to daily ET flux. ET at the Boise Hydrogeophysical Research Site (BHRS), a riparian zone in a temperate, semiarid environment, is calculated using a radiation-based method to provide …
Compressional And Em Wave Velocity Anisotropy In A Temperate Glacier Due To Basal Crevasses, And Implications For Water Content Estimation, John H. Bradford, Joshua Nichols, Joel T. Harper, Toby Meierbachtol
Compressional And Em Wave Velocity Anisotropy In A Temperate Glacier Due To Basal Crevasses, And Implications For Water Content Estimation, John H. Bradford, Joshua Nichols, Joel T. Harper, Toby Meierbachtol
CGISS Publications and Presentations
We have conducted a series of experiments designed to investigate elastic and electromagnetic (EM) velocity anisotropy associated with a preferentially aligned fracture system on a temperate valley glacier in south-central Alaska, USA. Measurements include a three-dimensional compressional wave (P-wave) seismic reflection survey conducted over a 300m × 300m survey patch, with uniform source grid and static checkerboard receiver pattern. Additionally, we acquired a multi-azimuth, multi-offset, polarimetric ground-penetrating radar (GPR) reflection experiment in a wagon-wheel geometry with 94° of azimuthal coverage. Results show azimuthal variation in the P-wave normal-moveout velocity of >3% (3765 and 3630ms-1 in the fast and slow …