Preliminary results of trench mapping at the site of prospective surface facilities for the potential Yucca Mountain repository, Nevada
- Geomatrix Consultants, San Francisco, CA (United States)
Mapping and trenching studies are yielding data needed to evaluate the surface faulting potential within Midway Valley, a half graben bounded by west-dipping normal faults on the northeast margin of Yucca Mountain. These studies document the presence of two north-trending zones of fractures within Quaternary deposits along the west-central part of the Midway Valley half-graben block. The westernmost zone of fractures, located along the eastern base of Exile Hill, overlies a complex zone of bedrock faulting and may be related to an apparent down-on-the-east step in the contact between bedrock and colluvium. Fractures striking [approximately]N15E extend upwards from this apparent bedrock step through early ( ) to middle ( ) Pleistocene colluvium. The fractures do not extend into the overlying late Pleistocene colluvium. No vertical or lateral separation of the probably middle to late Pleistocene colluvium across fractures can be detected with a resolution of 5 cm or less in most cases. The Quaternary deposits are much thicker along the eastern zone of fractures and bedrock was not exposed. The presence of continuous thin layers within the alluvial strata demonstrate the absence of any detectable vertical or lateral separation of the middle ( ) Pleistocene deposits across the fractures within the eastern zone with a high degree of confidence. The results of the authors studies indicate that faults within the west-central part of the Midway Valley structural block have had little or no displacement since at least the mid Quaternary. Therefore, potential for surface fault rupture in this area is extremely low.
- OSTI ID:
- 5190820
- Report Number(s):
- CONF-9305259--
- Journal Information:
- Geological Society of America, Abstracts with Programs; (United States), Journal Name: Geological Society of America, Abstracts with Programs; (United States) Vol. 25:5; ISSN GAAPBC; ISSN 0016-7592
- Country of Publication:
- United States
- Language:
- English
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12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES
54 ENVIRONMENTAL SCIENCES
540250 -- Environment
Terrestrial-- Site Resource & Use Studies-- (1990-)
58 GEOSCIENCES
580000 -- Geosciences
DEVELOPED COUNTRIES
EARTHQUAKES
GEOLOGIC FAULTS
GEOLOGIC FRACTURES
GEOLOGIC STRUCTURES
GEOLOGY
MAPPING
MATERIALS
MOUNTAINS
NEVADA
NORTH AMERICA
NUCLEAR FACILITIES
RADIOACTIVE MATERIALS
RADIOACTIVE WASTE FACILITIES
RADIOACTIVE WASTES
RISK ASSESSMENT
SEISMIC EVENTS
SEISMICITY
SITE CHARACTERIZATION
USA
WASTES
YUCCA MOUNTAIN