Geologic Characterization of Yucca Flat, Nevada, Using the Seismic Hammer™
WHAT: Monthly Dinner Meeting
WHEN: Thursday, March 3, 2016
WHERE: Ramada Reno Hotel
1000 East 6th Street, Reno, NV 89512
DETAILS: Hosted Cocktail Reception 6:30, Skyline Bar, 14th Floor
Dinner Served at 7:00 PM
NPGS Members $20, Non-Members $23, Students $10
SPEAKER: Robert E Abbott, Geophysicist, Sandia National Laboratories, Albuquerque, NM
TOPIC: Geologic Characterization of Yucca Flat, Nevada, Using the Seismic Hammer™
ABSTRACT: I present analysis of a multi-component, multi-channel, active-source seismic dataset acquired at the Nevada National Security Site (formerly the Nevada Test Site) using a prototype 13,000-kg weight-drop source. The purpose of the test was to determine the suitability of the source, called the Seismic Hammer™, for basin-scale characterization of Yucca Flat, Nevada. The source generates seismic energy by lifting the mass 1.5 meters before dropping it on a 1.8-m diameter plate. This results in over 190,000 Joules of potential energy being released. My results show that this results in ground motions similar to those produced by 20-kg of TNT equivalent explosives.
Two intersecting linear transects, 24-km and 14-km long, were acquired in 2015 with the goal of characterizing seismic propagation characteristics and geologic structure in advance of Phase II of the Source Physics Experiments (SPE). The goal of SPE is to use a series of underground chemical explosions at Yucca Flat to understand the mechanisms of shear wave generation from underground explosions. Shear-wave energy content is one major discriminant between earthquake and explosion sources and forms the basis of algorithms designed to monitor for worldwide nuclear tests.
My analysis shows that the Seismic Hammer™ is a source with unique properties and was well suited to data acquisition at Yucca Flat. Unlike vibrator sources, the Hammer produces significant energy below 2 Hz, allowing for usable data at source-receiver offsets as far as 11 km. Another benefit, in contrast to explosives, is the ability to hit multiple times at the same source point and stack the data, increasing the signal-to-noise-ratio. P-wave velocity structure was constrained to 2.5-km depth, well below the Paleozoic basement underlying the basin. Correlation of velocity structure to the known geology (Yucca Flat has thousands of boreholes due to underground nuclear testing) is excellent. S-Wave velocity structure was also recovered using the Refraction-Microtremor (ReMi) method. The quality of the shear-wave data was inversely proportional to the proximity to old nuclear tests.
Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-AC04-94AL85000.
BIOGRAPHY: Robert Abbott is a Principal Member of the Technical Staff at Sandia National Laboratories in Albuquerque, New Mexico. He received a Bachelor of Science in Physics in 1995, and a Ph.D. in Geophysics in 2001 from the University of Nevada, Reno. His dissertation (directed by John Louie) focused, in part, on the basin structure of southern Dixie Valley, Nevada. At Sandia since 2001, Dr. Abbott has primarily worked on issues surrounding explosion source phenomenology, seismic nuclear monitoring, nuclear nonproliferation, and geophysical characterization. Much of his work has taken place at the Nevada National Security Site (NNSS, formerly the Nevada Test Site).
Cocktail Reception Hosted by: HK Exploration, LLC; Oil & Gas Exploration Services, 1101 Colorado St., Boulder City, NV 89006
Please RSVP by Tuesday March 1 for the Dinner Meeting here.
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