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Description: In Gubbio, Italy, a l em layer of clay between extensive limestone formations marks the boundary between the Cretaceous and Tertiary Periods. This clay layer was known to have been deposited about 65 million years ago when many life forms became extinct, but the length of time associated with the deposition was not known. In an attempt to measure this time with normally deposited meteoritic material as a clock, extensive measurements of iridium abundances (and those of many other elements) were made on the Gubbio rocks. Neutron activation analysis was the principal tool used in these studies. About 50 elements are searched for in materials like the earth's crust, about 40 are detected and about 30 are measured with useful precision. We were not able to determine exactly how long the clay deposition took. Instead the laboratory studies on the chemical and physical nature of the Cretaceous-Tertiary boundary led to the theory that an asteroid collision with the earth was responsible for the extinction of many forms of life including the dinosaurs.
Date: September 1, 1980
Creator: Asaro, Frank; Michel, Helen V.; Alvarez, Luis W. & Alvarez, Walter
Partner: UNT Libraries Government Documents Department

Collaborative Research: Robust Climate Projections and Stochastic Stability of Dynamical Systems

Description: The project was completed along the lines of the original proposal, with additional elements arising as new results were obtained. The originally proposed three thrusts were expanded to include an additional, fourth one. (i) The e#11;ffects of stochastic perturbations on climate models have been examined at the fundamental level by using the theory of deterministic and random dynamical systems, in both #12;nite and in#12;nite dimensions. (ii) The theoretical results have been implemented #12;first on a delay-diff#11;erential equation (DDE) model of the El-Nino/Southern-Oscillation (ENSO) phenomenon. (iii) More detailed, physical aspects of model robustness have been considered, as proposed, within the stripped-down ICTP-AGCM (formerly SPEEDY) climate model. This aspect of the research has been complemented by both observational and intermediate-model aspects of mid-latitude and tropical climate. (iv) An additional thrust of the research relied on new and unexpected results of (i) and involved reduced-modeling strategies and associated prediction aspects have been tested within the team's empirical model reduction (EMR) framework. Finally, more detailed, physical aspects have been considered within the stripped-down SPEEDY climate model. The results of each of these four complementary e#11;fforts are presented in the next four sections, organized by topic and by the team members concentrating on the topic under discussion.
Date: October 13, 2011
Creator: Ghil, Michael; McWilliams, James; Neelin, J. David; Zaliapin, Ilya; Chekroun, Mickael; Kondrashov, Dmitri et al.
Partner: UNT Libraries Government Documents Department

Geochemical and Strontium Isotope Characterization of Produced Waters from Marcellus Shale Natural Gas Extraction

Description: Extraction of natural gas by hydraulic fracturing of the Middle Devonian Marcellus Shale, a major gas-bearing unit in the Appalachian Basin, results in significant quantities of produced water containing high total dissolved solids (TDS). We carried out a strontium (Sr) isotope investigation to determine the utility of Sr isotopes in identifying and quantifying the interaction of Marcellus Formation produced waters with other waters in the Appalachian Basin in the event of an accidental release, and to provide information about the source of the dissolved solids. Strontium isotopic ratios of Marcellus produced waters collected over a geographic range of ∼375 km from southwestern to northeastern Pennsylvania define a relatively narrow set of values (εSr SW = +13.8 to +41.6, where εSr SW is the deviation of the 87Sr/86Sr ratio from that of seawater in parts per 104); this isotopic range falls above that of Middle Devonian seawater, and is distinct from most western Pennsylvania acid mine drainage and Upper Devonian Venango Group oil and gas brines. The uniformity of the isotope ratios suggests a basin-wide source of dissolved solids with a component that is more radiogenic than seawater. Mixing models indicate that Sr isotope ratios can be used to sensitively differentiate between Marcellus Formation produced water and other potential sources of TDS into ground or surface waters.
Date: February 24, 2012
Creator: Elizabeth C. Chapman,† Rosemary C. Capo,† Brian W. Stewart,*,† Carl S. Kirby,‡ Richard W. Hammack,§ Karl T. Schroeder,§ and Harry M. Edenborn
Partner: UNT Libraries Government Documents Department

MITAS-2009 Expedition, U.S. Beaufort Shelf and Slope—Lithostratigraphy Data Report

Description: The volume of methane released through the Arctic Ocean to the atmosphere and its potential role in the global climate cycle have increasingly become the focus of studies seeking to understand the source and origin of this methane. In 2009, an international, multi-disciplinary science party aboard the U.S. Coast Guard icebreaker Polar Sea successfully completed a trans-U.S. Beaufort Shelf expedition aimed at understanding the sources and volumes of methane across this region. Following more than a year of preliminary cruise planning and a thorough site evaluation, the Methane in the Arctic Shelf/Slope (MITAS) expedition departed from the waters off the coast of Barrow, Alaska in September 2009. The expedition was organized with an international shipboard science team consisting of 33 scientists with the breadth of expertise necessary to meet the expedition goals. NETL researchers led the expedition’s initial core processing and lithostratigraphic evaluations, which are the focus of this report. This data report is focused on the lithostratigraphic datasets from the recovered vibra cores and piston cores. Operational information about the piston and vibra cores such as date acquired, core name, total length, water depth, and geographic location is provided. Once recovered, gas samples were immediately collected from cores. In addition, each core was run through the Geotek multi-sensor core logger for magnetic susceptibility, P-wave velocity, resistivity, and gamma-density measurements (Rose et al., 2010). After the samples and measurements were completed, the cores were split into working and archive halves. Visual core descriptions of the archive half was completed for each core. Samples for shipboard smear slides, coarse fractions, and XRD analyses were collected, as well as corresponding samples for post-cruise grain size analysis from the working half of each core. Line scan images of the split core surfaces were collected post-expedition. The methods used to characterize the lithostratigraphy of ...
Date: September 17, 2012
Creator: Rose, K.; Johnson, J.E.; Phillips, S.C.; Smith, J.; Reed, A.; Disenhof, C. et al.
Partner: UNT Libraries Government Documents Department


Description: Topics covered include: Failure At High Confining Pressure; Fluid-assisted Slip, Earthquakes & Fracture; Reaction-driven Cracking; Fluid Transport, Deformation And Reaction; Localized Fluid Transport And Deformation; Earthquake Mechanisms; Subduction Zone Dynamics And Crustal Growth.
Date: August 24, 2012
Creator: Kelemen, Peter
Partner: UNT Libraries Government Documents Department


Description: We conduct a detailed test of a recently developed technique, CAPloc, in recovering source parameters from a few stations against results from a large broadband network. The method uses a library of 1D Green’s functions which are broken into segments and matched to waveform observations with adjustable timing shifts. These shifts can be established by calibration against a distribution of well-located earthquake and assembled in tomographic images for predicting various phase-delays. Synthetics generated from 2D cross-sections through these models indicates that 1D synthetic waveforms are sufficient in modeling but simply shifted in time for hard-rock sites. This simplification allows the source inversion for both mechanism and location to be easily obtained by grid search. We test one-station mechanisms for 160 events against the array for both PAS and GSC which have data since 1960. While one station solutions work well (about 90%), joint solutions produce more reliable and defensible results. Inverting for both mechanism and location also works well except for certain difficult paths that cross deep basins or propagate along mountain ridges.
Date: December 10, 2007
Creator: Helmberger, Donald V.; Tromp, Jeroen & Rodgers, Arthur J.
Partner: UNT Libraries Government Documents Department


Description: Earthquake source parameters underpin several aspects of nuclear explosion monitoring. Such aspects are: calibration of moment magnitudes (including coda magnitudes) and magnitude and distance amplitude corrections (MDAC); source depths; discrimination by isotropic moment tensor components; and waveform modeling for structure (including waveform tomography). This project seeks to improve methods for and broaden the applicability of estimating source parameters from broadband waveforms using the Cut-and-Paste (CAP) methodology. The CAP method uses a library of Green’s functions for a one-dimensional (1D, depth-varying) seismic velocity model. The method separates the main arrivals of the regional waveform into 5 windows: Pnl (vertical and radial components), Rayleigh (vertical and radial components) and Love (transverse component). Source parameters are estimated by grid search over strike, dip, rake and depth and seismic moment or equivalently moment magnitude, MW, are adjusted to fit the amplitudes. Key to the CAP method is allowing the synthetic seismograms to shift in time relative to the data in order to account for path-propagation errors (delays) in the 1D seismic velocity model used to compute the Green’s functions. The CAP method has been shown to improve estimates of source parameters, especially when delay and amplitude biases are calibrated using high signal-to-noise data from moderate earthquakes, CAP+.
Date: June 17, 2008
Creator: Helmberger, Donald V.; Tromp, Jeroen & Rodgers, Arthur J.
Partner: UNT Libraries Government Documents Department


Description: Comprehensive test ban monitoring in terms of location and discrimination has progressed significantly in recent years. However, the characterization of sources and the estimation of low yields remains a particular challenge.
Date: June 30, 2007
Creator: Helmberger, Donald V.; Tromp, Jeroen & Rodgers, Arthur J.
Partner: UNT Libraries Government Documents Department

Fractional Calculus in Hydrologic Modeling: A Numerical Perspective

Description: Fractional derivatives can be viewed either as a handy extension of classical calculus or, more deeply, as mathematical operators defined by natural phenomena. This follows the view that the diffusion equation is defined as the governing equation of a Brownian motion. In this paper, we emphasize that fractional derivatives come from the governing equations of stable Levy motion, and that fractional integration is the corresponding inverse operator. Fractional integration, and its multi-dimensional extensions derived in this way, are intimately tied to fractional Brownian (and Levy) motions and noises. By following these general principles, we discuss the Eulerian and Lagrangian numerical solutions to fractional partial differential equations, and Eulerian methods for stochastic integrals. These numerical approximations illuminate the essential nature of the fractional calculus.
Date: January 1, 2012
Creator: Benson, David A.; Meerschaert, Mark M. & Revielle, Jordan
Partner: UNT Libraries Government Documents Department

Final technical report for the Award DE-FG02-08ER64574, with list of 30 refereed journal articles that acknowledge support from this award.

Description: In this project, we focused on applications of the new warm-rain and ice microphysics schemes to simulate various cloud systems. The overall goal was either to evaluate and improve specific aspects of the schemes (through comparisons with ARM/ASR observations) or to understand the coupling between aerosols, cloud microphysics and cloud dynamics in variety of situations. These studies are relevant to the indirect impact of atmospheric aerosols on climate. Below we report on selected key aspects of the research and then list all peer-reviewed papers that acknowledge support from this grant. Overall, studies partially supported by this grant resulted in 30 peer-reviewed publications (listed below), several dozens of conference presentations (including posters and oral presentations at the ASR Science Team Meetings), and two PhD dissertations. More detailed summaries of our accomplishments are included in yearly reports. Here we summarize only major efforts.
Date: April 2, 2012
Creator: Grabowski, Wojciech W.
Partner: UNT Libraries Government Documents Department

Final Report for DOE grant DE-FG02-07ER64432 "New Grid and Discretization Technologies for Ocean and Ice Simulations"

Description: The work reported is in pursuit of these goals: high-quality unstructured, non-uniform Voronoi and Delaunay grids; improved finite element and finite volume discretization schemes; and improved finite element and finite volume discretization schemes. These are sought for application to spherical and three-dimensional applications suitable for ocean, atmosphere, ice-sheet, and other climate modeling applications.
Date: March 12, 2013
Creator: Gunzburger, Max
Partner: UNT Libraries Government Documents Department