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Articles 1 - 13 of 13
Full-Text Articles in Physical Sciences and Mathematics
Overpumping Leads To California Groundwater Arsenic Threat, Ryan G. Smith, Rosemary Knight, Scott Fendorf
Overpumping Leads To California Groundwater Arsenic Threat, Ryan G. Smith, Rosemary Knight, Scott Fendorf
Geosciences and Geological and Petroleum Engineering Faculty Research & Creative Works
Water resources are being challenged to meet domestic, agricultural, and industrial needs. To complement finite surface water supplies that are being stressed by changes in precipitation and increased demand, groundwater is increasingly being used. Sustaining groundwater use requires considering both water quantity and quality. A unique challenge for groundwater use, as compared with surface water, is the presence of naturally occurring contaminants within aquifer sediments, which can enter the water supply. Here we find that recent groundwater pumping, observed through land subsidence, results in an increase in aquifer arsenic concentrations in the San Joaquin Valley of California. By comparison, historic …
St. Louis Area Earthquake Hazards Mapping Project: Seismic And Liquefaction Hazard Maps, Chris H. Cramer, Robert A. Bauer, Jaewon Chung, J. David Rogers, Larry Pierce, Vicki Voigt, Brad Mitchell, David Gaunt, Robert A. Williams, David J. Hoffman, Gregory L. Hempen, Phyllis J. Steckel, Oliver Salz Boyd, Connor M. Watkins, Kathleen B. Tucker, Natasha S. Mccallister
St. Louis Area Earthquake Hazards Mapping Project: Seismic And Liquefaction Hazard Maps, Chris H. Cramer, Robert A. Bauer, Jaewon Chung, J. David Rogers, Larry Pierce, Vicki Voigt, Brad Mitchell, David Gaunt, Robert A. Williams, David J. Hoffman, Gregory L. Hempen, Phyllis J. Steckel, Oliver Salz Boyd, Connor M. Watkins, Kathleen B. Tucker, Natasha S. Mccallister
Geosciences and Geological and Petroleum Engineering Faculty Research & Creative Works
We present probabilistic and deterministic seismic and liquefaction hazard maps for the densely populated St. Louis metropolitan area that account for the expected effects of surficial geology on earthquake ground shaking. Hazard calculations were based on a map grid of 0.005°, or about every 500 m, and are thus higher in resolution than any earlier studies. To estimate ground motions at the surface of the model (e.g., site amplification), we used a new detailed near-surface shear-wave velocity model in a 1D equivalent- linear response analysis. When compared with the 2014 U.S. Geological Survey (USGS) National Seismic Hazard Model, which uses …
A Uniform Database Of Teleseismic Shear-Wave Splitting Measurements For The Western And Central United States: December 2014 Update, Bin B. Yang, Kelly H. Liu, Haider H. Dahm, Stephen S. Gao
A Uniform Database Of Teleseismic Shear-Wave Splitting Measurements For The Western And Central United States: December 2014 Update, Bin B. Yang, Kelly H. Liu, Haider H. Dahm, Stephen S. Gao
Geosciences and Geological and Petroleum Engineering Faculty Research & Creative Works
We present a new version of a shear-wave splitting (SWS) database for the western and central United States (WCUS) using broadband seismic data recorded up to the end of 2014 to update a previous version that used data recorded prior to the end of 2012, when the USArray Transportable Array stations were still recording in the easternmost region of theWCUS. A total of 7452 pairs of additional measurements recorded by 1202 digital broadband seismic stations are obtained, and all the measurements in the previous database are rechecked. The resulting uniform SWS database contains a total of 23,448 pairs of well-defined …
Seismic-Hazard Map Of Southeast Missouri And Likely Magnitude Of The February 1812 New Madrid Earthquake, Jaewon Chung, J. David Rogers
Seismic-Hazard Map Of Southeast Missouri And Likely Magnitude Of The February 1812 New Madrid Earthquake, Jaewon Chung, J. David Rogers
Geosciences and Geological and Petroleum Engineering Faculty Research & Creative Works
The New Madrid seismic zone lies beneath the upper Mississippi Embayment, straddling the border between southeastern Missouri and northwestern Tennessee. In late 1811 and early 1812, it produced five earthquakes of magnitudes >6.5, violently shaking the central and eastern United States (CEUS). Its magnitude and recurrence are of concern to today's central United States regions. By considering the effects of local geology, deterministic scenario maps (Mw 7.3 and 7.7) were produced for ground motions intended to simulate the 7 February 1812 event (NM3), which was the largest felt. These maps include spatial estimates of peak ground acceleration and of …
Mantle Transition Zone Discontinuities Beneath The Contiguous United States, Stephen S. Gao, Kelly H. Liu
Mantle Transition Zone Discontinuities Beneath The Contiguous United States, Stephen S. Gao, Kelly H. Liu
Geosciences and Geological and Petroleum Engineering Faculty Research & Creative Works
Using over 310,000 high-quality radial receiver functions recorded by the USArray and other seismic stations in the contiguous United States, the depths of the 410 km and 660 km discontinuities (d410 and d660) are mapped in over 1,000 consecutive overlapping circles with a radius of 1⁰. The average mantle transition zone (MTZ) thickness for both the western and central/eastern U.S. is within 3 km from the global average of 250 km, suggesting an overall normal MTZ temperature beneath both areas. The Pacific Coast Ranges and the southern Basin and Range Province are underlain by a depressed d410, indicating higher-than-normal temperature …
A Uniform Database Of Teleseismic Shear Wave Splitting Measurements For The Western And Central United States, Kelly H. Liu, Ahmed Elsheikh, Awas Lemnifi, Uranbaigal Purevsuren, Melissa Ray, Hesham Refayee, Bin B. Yang, Youqiang Yu, Stephen S. Gao
A Uniform Database Of Teleseismic Shear Wave Splitting Measurements For The Western And Central United States, Kelly H. Liu, Ahmed Elsheikh, Awas Lemnifi, Uranbaigal Purevsuren, Melissa Ray, Hesham Refayee, Bin B. Yang, Youqiang Yu, Stephen S. Gao
Geosciences and Geological and Petroleum Engineering Faculty Research & Creative Works
We present a shear wave splitting (SWS) database for the western and central United States as part of a lasting effort to build a uniform SWS database for the entire North America. The SWS measurements were obtained by minimizing the energy on the transverse component of the PKS, SKKS, and SKS phases. Each of the individual measurements was visually checked to ensure quality. This version of the database contains 16,105 pairs of splitting parameters. The data used to generate the parameters were recorded by 1774 digital broadband seismic stations over the period of 1989-2012, and represented all the available data …
Seismic Site Classifications For The St. Louis Urban Area, Jaewon Chung, J. David Rogers
Seismic Site Classifications For The St. Louis Urban Area, Jaewon Chung, J. David Rogers
Geosciences and Geological and Petroleum Engineering Faculty Research & Creative Works
Regional National Earthquake Hazards Reduction Program (NEHRP) soil class maps have become important input parameters for seismic site characterization and hazard studies. The broad range of shallow shear-wave velocity (VS30, the average shear-wave velocity in the upper 30 m) measurements in the St. Louis area results in significant uncertainties between the actual spot values and the averaged values used to assign NEHRP soil classes for regional seismic hazard studies. In the preparation of an NEHRP site classification map of the St. Louis urban area, we analyzed 92 shear-wave velocity (VS) measurements, supplemented by 1400+ standard penetration …
Magnetic Susceptibility As A Proxy For Investigating Microbially Mediated Iron Reduction, Farag M. Mewafy, Estella A. Atekwana, D. Dale Werkema, Lee D. Slater, Dimitrios Ntarlagiannis, Andre Revil, Magnus E. Skold, Geoffrey N. Delin
Magnetic Susceptibility As A Proxy For Investigating Microbially Mediated Iron Reduction, Farag M. Mewafy, Estella A. Atekwana, D. Dale Werkema, Lee D. Slater, Dimitrios Ntarlagiannis, Andre Revil, Magnus E. Skold, Geoffrey N. Delin
Geosciences and Geological and Petroleum Engineering Faculty Research & Creative Works
We investigated magnetic susceptibility (MS) variations in hydrocarbon contaminated sediments. Our objective was to determine if MS can be used as an intrinsic bioremediation indicator due to the activity of iron-reducing bacteria. A contaminated and an uncontaminated core were retrieved from a site contaminated with crude oil near Bemidji, Minnesota and subsampled for MS measurements. The contaminated core revealed enriched MS zones within the hydrocarbon smear zone, which is related to iron-reduction coupled to oxidation of hydrocarbon compounds and the vadose zone, which is coincident with a zone of methane depletion suggesting aerobic or anaerobic oxidation of methane is coupled …
In-Situ Apparent Conductivity Measurements And Microbial Population Distribution At A Hydrocarbon-Contaminated Site, Estella A. Atekwana, D. Dale Werkema, Joseph W. Duris, Silvia Rossbach, Eliot A. Atekwana, William A. Sauck, Daniel P. Cassidy, Jay Means, Franklyn D. Legall
In-Situ Apparent Conductivity Measurements And Microbial Population Distribution At A Hydrocarbon-Contaminated Site, Estella A. Atekwana, D. Dale Werkema, Joseph W. Duris, Silvia Rossbach, Eliot A. Atekwana, William A. Sauck, Daniel P. Cassidy, Jay Means, Franklyn D. Legall
Geosciences and Geological and Petroleum Engineering Faculty Research & Creative Works
We investigated the bulk electrical conductivity and microbial population distribution in sediments at a site contaminated with light nonaqueous-phase liquid (LNAPL). The bulk conductivity was measured using in-situ vertical resistivity probes; the most probable number method was used to characterize the spatial distribution of aerobic heterotrophic and oil-degrading microbial populations. The purpose of this study was to assess if high conductivity observed at aged LNAPL-impacted sites may be related to microbial degradation of LNAPL. The results show higher bulk conductivity coincident with LNAPL-impacted zones, in contrast to geoelectrical models that predict lower conductivity in such zones. The highest bulk conductivity …
Field-Scale Estimation Of Volumetric Water Content Using Ground-Penetrating Radar Ground Wave Techniques, Katherine R. Grote, Susan Sharpless Hubbard, Yoram N. Rubin
Field-Scale Estimation Of Volumetric Water Content Using Ground-Penetrating Radar Ground Wave Techniques, Katherine R. Grote, Susan Sharpless Hubbard, Yoram N. Rubin
Geosciences and Geological and Petroleum Engineering Faculty Research & Creative Works
Ground-penetrating radar (GPR) ground wave techniques were applied to estimate soil water content in the uppermost ∼10 cm of a 3 acre California vineyard several times over 1 year. We collected densely spaced GPR travel time measurements using 900 and 450 MHz antennas and analyzed these data to estimate water content. The spatial distribution of water content across the vineyard did not change significantly with time, although the absolute water content values varied seasonally and with irrigation. The GPR estimates of water content were compared to gravimetric water content, time domain reflectometry, and soil texture measurements. The comparisons of GPR-derived …
Sequence Stratigraphy And Depositional Facies Of Lower Ordovician Cyclic Carbonate Rocks, Southern Missouri, U.S.A., Robert Brandon Overstreet, Francisca Oboh-Ikuenobe, Jay M. Gregg
Sequence Stratigraphy And Depositional Facies Of Lower Ordovician Cyclic Carbonate Rocks, Southern Missouri, U.S.A., Robert Brandon Overstreet, Francisca Oboh-Ikuenobe, Jay M. Gregg
Geosciences and Geological and Petroleum Engineering Faculty Research & Creative Works
Lower Ordovician cyclic carbonate strata of southern Missouri were deposited in a warm, shallow, epeiric sea on a fully aggraded carbonate platform. Sedimentological characteristics distinguish the Jefferson City and Cotter dolomites from the underlying Gasconade and Roubidoux formations. Mixed carbonate-siliciclastic sedimentation characterizes the Roubidoux Formation, with sandstones accounting for up to 60% of sedimentation. The Gasconade, Jefferson City, and Cotter dolomites exhibit an increased occurrence of chalcedonic chert nodules in very similar shape and texture to the gypsum and anhydrite nodules common on modern sabkha supratidal flats. Casts of halite and ghosts of gypsum laths also exist in the Jefferson …
Analysis Of Deformation Data At Parkfield, California: Detection Of A Long-Term Strain Transient, Stephen S. Gao, Paul G. Silver, Alan T. Linde
Analysis Of Deformation Data At Parkfield, California: Detection Of A Long-Term Strain Transient, Stephen S. Gao, Paul G. Silver, Alan T. Linde
Geosciences and Geological and Petroleum Engineering Faculty Research & Creative Works
Analysis of more than a decade of high-quality data, particularly those from the two-color electronic distance meter (EDM), in the Parkfield, California, area reveals a significant transient in slip rate along the San Andreas Fault. This transient consists of an increase in fault slip rate of 3.3 ± 0.9 mm/yr during 1993.0 to 1998.0. The most reliable fault creep instruments show a comparable increase in slip rate, suggesting that the deformation is localized to the fault which breaks the surface. There was also an increase in precipitation around 1993. It is unlikely, however, that this anomaly is due directly to …
Dolomitization And Dolomite Neomorphism: Trenton And Black River Limestones (Middle Ordovician) Northern Indiana, U.S.A., M. I N Chan, Jay M. Gregg, Kevin L. Shelton
Dolomitization And Dolomite Neomorphism: Trenton And Black River Limestones (Middle Ordovician) Northern Indiana, U.S.A., M. I N Chan, Jay M. Gregg, Kevin L. Shelton
Geosciences and Geological and Petroleum Engineering Faculty Research & Creative Works
The Trenton and Black River Limestones are dolomitized extensively along the axis of the Kankakee Arch in Indiana, with the proportion of dolomite decreasing to the south and southeast of the arch. Planar and nonplanar dolomite replacement textures and rhombic (type 1) and saddle (type 2) void-filling dolomite cements are present. Three stages of dolomitization, involving different fluids, are inferred on the basis of petrographic and geochemical characteristics of the dolomites. Nonferroan planar dolomite has relatively high δ18O values (-1.8 to -6.1‰ PDB) and has 87Sr/86Sr ratios (0.70833 to 0.70856) that overlap those of Middle Ordovician seawater. …