Characteristics of Fault Zones in Volcanic Rocks Near Yucca Flat, Nevada Test Site, Nevada

Technical Report · Tue Nov 27 04:00:00 EST 2007

DOI:https://doi.org/10.2172/920108· OSTI ID:920108

Sweetkind, Donald ^[1]; Drake, II, Ronald M

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1. USGS

During 2005 and 2006, the USGS conducted geological studies of fault zones at surface outcrops at the Nevada Test Site. The objectives of these studies were to characterize fault geometry, identify the presence of fault splays, and understand the width and internal architecture of fault zones. Geologic investigations were conducted at surface exposures in upland areas adjacent to Yucca Flat, a basin in the northeastern part of the Nevada Test Site; these data serve as control points for the interpretation of the subsurface data collected at Yucca Flat by other USGS scientists. Fault zones in volcanic rocks near Yucca Flat differ in character and width as a result of differences in the degree of welding and alteration of the protolith, and amount of fault offset. Fault-related damage zones tend to scale with fault offset; damage zones associated with large-offset faults (>100 m) are many tens of meters wide, whereas damage zones associated with smaller-offset faults are generally a only a meter or two wide. Zeolitically-altered tuff develops moderate-sized damage zones whereas vitric nonwelded, bedded and airfall tuff have very minor damage zones, often consisting of the fault zone itself as a deformation band, with minor fault effect to the surrounding rock mass. These differences in fault geometry and fault zone architecture in surface analog sites can serve as a guide toward interpretation of high-resolution subsurface geophysical results from Yucca Flat.

• Research Organization: United States Geological Survey - Nevada, Henderson, Nevada
• Sponsoring Organization: USDOE - National Nuclear Security Administration (NNSA)
• DOE Contract Number: AI52-07NA28100
• OSTI ID: 920108
• Report Number(s): OFR 2007-1293
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
ARCHITECTURE
Characteristics
DEFORMATION
FORMATION DAMAGE
Fault Zones
GEOMETRY
NEVADA TEST SITE
Nevada
Nevada Test Site
TUFF
VOLCANIC ROCKS
Volcanic Rock
WELDING
Yucca Flat