EES Focus AreasEES Group Pages |
Recent EES Division HighlightsMay 2nd, 2008 Presentations at the Seismological Society of America Meeting LANL researchers from EES hosted and presented at the recent SSA meeting in Santa Fe. Jamie Gardner (EES-9) gave an invited talk at the special session "Extensional Seismotectonics of the Rio Grande Rift and its Margins". The talk, "Paleoseismology and Geology of the Pajarito Fault System, Rio Grande Rift, New Mexico," provided a synthesis of results from about 20 years of research regarding seismic hazards at LANL. The Pajarito Fault System which forms the western boundary of LANL presents a potentially serious earthquake hazard to the Laboratory. Co-authors on the EES Seismic Geology Team are C. Lewis, S. Reneau, and E. Schultz-Fellenz 
(Click thumbnail to view larger image.) EES-11's Chris Bradley chaired and gave a presentation in a session entitled "Earthquakes and Society: Developing Community Resiliency through Earthquake Scenarios". Chris' talk, "Site-specific Rock Mechanical and Slope Stability Analysis of the BSL-3 Facility" addressed the earthquake response of the new Biological Safety Laboratory (BSL-3) to the newly released Probabilistic Seismic Hazard Analysis (PSHA) for LANL. The study included 3-D numerical modeling of the fractured and jointed Bandelier Tuff to synthetic earthquakes. Coauthors of the study included Tom Houston (D-5), Peter Roberts, and David Steedman (EES-11), and Claudia Lewis (EES-9). April 28, 2008 Volcanic Risk Assessment at Yucca Mountain Gordon Keating, Greg Valentine, Don Krier, and Frank Perry of EES-9 published a paper that quantifies key parameters used to model eruption scenarios for volcanic risk assessment at the planned Yucca Mountain high-level radioactive waste repository in Nevada. "Shallow Plumbing Systems for Small-volume Basaltic Volcanoes" summarizes field work of eroded analogue volcanoes that were used to characterize the geometry of potential future basaltic conduits through the Yucca Mountain repository. The paper compares field measurements to theoretical considerations of conduit flow in order to draw general conclusions about the size and shape of potential conduits at repository depth (ca. 300 m) and the nature of the transition from dike to conduit at shallow depths. Quantification of the size and geometry of basaltic conduits has not been done previously at this depth range. This kind of information is critical in the analysis of consequences of a potential basaltic eruption through the waste repository. Given the explicit layout of storage tunnels and the shape and disposition of waste packages, the size and geometry of a magmatic conduit developing at the repository horizon has direct bearing on the number of waste packages damaged and the amount of waste released during a potential volcanic eruption. The quantification of magma conduit geometry developed in this paper provides direct input to the eruptive case submodel of the Yucca Mountain Total System Performance Assessment (TSPA). In a broader sense, the comparison of field observations to conduit geometries developed in the numerical model supports the concept of lithostatic-pressure balanced flow conditions put forth by Wilson and Head (1981). DOE's Yucca Mountain Project funded the research. 
(Click thumbnail to view larger image.) The paper is published in the Bulletin of Volcanology 70: 563-582 (2008). April 12, 2008 LANL Hosts Annual Meeting of the Seismological Society of America (SSA) The world's leading seismologists gathered in Santa Fe, NM for the 102nd Annual meeting of the SSA. LANL was the host institute for the meeting in cooperation with other Rio Grande institutions including Sandia National Laboratories, New Mexico Tech, and University of Texas at El Paso. Charlotte Rowe of EES-11 chaired the meeting. Approximately 500 national and international scientists attended. This meeting affords EES researchers the opportunity to present their research and participate in stimulating exchanges of the latest research on earthquakes, volcanoes, nuclear explosions, and more. Over 450 abstracts were received. Thirty EES researchers are authors or co-authors on 25 different research presentations. Six EES-11 staff members co-convened five of the special technical sessions...
 Many of the LANL presentations were the result of collaborations with industry, government organizations, and universities. Read more at the SSA web site. April 1, 2008 Multiscale Analysis Applicable to Field Scale Simulations A major problem in modeling natural porous media is obtaining an accurate description of their flow and transport behavior in spite of the intrinsic heterogeneity of geological formations. The modeling equations have coefficients that vary on scales that are small compared with the overall size of the domain of interest. Any accurate numerical solution of these models requires a very finely divided computational mesh, something that often is not feasible. Obtaining the macroscopic behavior of a given system can become computationally expensive even with modern supercomputers. Therefore, to analyze the system from a macrostructure point of view, it is desirable to simplify it in such a way that the phenomena of interest remain adequately described. The simplified equations are called homogenized equations, and the procedure of replacing the original system is called homogenization. Researchers Roseangela Svlercoski and Brayan Travis of EES-2 and T-7's James Hyman recently published a paper entitled "Analytical effective coefficient and a first-order approximation for linear flow through block permeability inclusions" in Computers & Mathematics with Applications, 55 (9), 2118-2133, (2008). These new results are applicable to idealized geometric form of inclusions in a main matrix. However, the extension to the general case is possible and it is ongoing work. The new results will allow multiscale numerical simulations for field scale applications which is also the new feature of the method. (Read more.) The LANL researchers have developed an approach that differs from the previous ones, by simplifying the numerics involved in such approximations. The approach has the enormous advantage of portability because it can be used with any existing elliptic solver. Below, Figure 1 shows a comparison of the analytic solution with square inclusion and the relevant numerical approximation. The two graphs agree well with each other but differ on the smoothness. The ultimate goal is to apply the method to multiphase systems in cases where diffusion is the driving process. A Chevron-LANL CRADA provided support for the work.  Left - Analytical solution with square inclusion. Right - Numerical approximation.
|
|