GIS Surface effects archive of underground nuclear detonations conducted at Yucca Flat and Pahute Mesa, Nevada Test Site, Nevada

Grasso, Dennis

doi:10.3133/ofr01272

Cited by 5 publications

(8 citation statements)

References 2 publications

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“…1). Surficial geologic mapping (Slate and others, 2000) and analysis of surface effects (Grasso, 2001) suggest the presence of small-offset faults. Geophysical surveys at this location were designed to investigate small-offset faults distant from the major mapped normal faults in the basin (T.H.…”

Section: Geologic Settingmentioning

confidence: 99%

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

Sweetkind¹,

Drake²

2007

Open-File Report

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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. Zeoliticallyaltered 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.

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Section: Geologic Settingmentioning

confidence: 99%

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

Sweetkind¹,

Drake²

2007

Open-File Report

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“…This resulted in a total of 750 underground nuclear detonations (including three crater detonations) in the study area (U.S. Department of Energy, 2000b). The surface of Yucca Flat is marked by hundreds of collapse sinks or subsidence craters that formed at the locations of underground nuclear detonations (Grasso, 2000(Grasso, , 2001Stoller-Navarro Joint Venture, 2009). Some of these collapse sinks in the central part of Yucca Flat are evident on the shaded-relief base map shown on figure 2.…”

Section: Description Of Study Areamentioning

confidence: 99%

“…Within minutes to days of the test, rock above the cavity collapses into the cavity forming a chimney (Pawloski and others, 2008). For many of the tests, the collapse chimney extends all the way to land surface, in which case, a collapse sink is formed (Grasso, 2001).…”

Section: Nuclear Testingmentioning

confidence: 99%

Conceptualization of the predevelopment groundwater flow system and transient water-level responses in Yucca Flat, Nevada National Security Site, Nevada

Fenelon¹,

Sweetkind²,

Elliott³

et al. 2012

Scientific Investigations Report

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“…The Yucca Fault is a north-striking, east-dipping, normal fault located in the eastern half of Yucca Flat (fig. 1), and it shows a meter-scale surface scarp and bedrock offsets of 200-400 m. Yucca Fault has distinct splays and step-overs in some locations, and it is also accompanied by many other smaller faults throughout the area (Grasso, 2001). In many cases, these smaller faults are anthropomorphic in nature, having been created by the testing of nuclear weapons at the site (see, for example, Barosh, 1968).…”

Section: Introductionmentioning

confidence: 99%

Electrical Resistivity and Seismic Surveys at the Nevada Test Site, Nevada, April 2007

Haines¹,

Burton²,

Sweetkind³

et al. 2008

Open-File Report

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In April 2007, the USGS collected direct-current (DC) electrical resistivity data and shear-(S) and compressional-(P) wave seismic data to provide new detail of previously mapped, overlapping fault splays at two administrative areas in the Nevada Test Site (NTS). In NTS Area 7, we collected twodimensional DC resistivity data along a transect crossing the Yucca Fault parallel to, and between, two transects along which resistivity data were collected in a previous study in 2006. In addition, we collected three-dimensional DC resistivity data in a grid that overlies part of the 2007 transect. The DC resistivity data show that the fault has a footwall that is more conductive than the hanging wall and an along-strike progression of the fault in a location where overlapping splays are present. Co-located with the northernmost of the two 2006 DC resistivity transects, we acquired S-and P-wave seismic data for both reflection and refraction processing. The S-wave data are corrupted by large amounts of converted (P-wave) energy likely due to the abundance of fractured caliche in the shallow subsurface. The P-wave data show minimal reflected energy, but they show clear refracted first arrivals. We have inverted these first arrival times to determine P-wave seismic velocity models. The seismic model for the transect in Area 7 shows low velocities extending to the base of the model at the location of the Yucca Fault, as well as low velocities at the eastern end of the transect, in the vicinity of the adjacent crater. These new surveys provide further detail about the geometry of the Yucca Fault in this location where it shows two overlapping splays. We collected P-and S-wave seismic data along a transect in the southern part of NTS Area 2, corresponding with the location of a 2006 DC resistivity transect that targeted a set of small faults identified with field mapping. Again, the S-wave data are difficult to interpret. The P-wave data show 1 clear first arrivals that we inverted, yielding a velocity model that shows lateral heterogeneity similar to the 2006 DC resistivity models. Finally, we collected P-wave data along a second transect in Area 2, located north of the first line and in an area of a very minor fault that was targeted by another 2006 DC resistivity survey. The P-wave refraction velocity model shows generally high velocities, with a zone of somewhat lower velocities in the central part of the transect. The position of the low velocity zone corresponds with the location of a minor fault, though it is unclear whether the two are related. Together, these results demonstrate the value of geophysical data for mapping the subsurface extent of faults. The 2007 DC resistivity data complement the 2006 data and provide important new detail of the overlapping fault splays. The seismic data demonstrate the ability of P-wave refraction methods to identify the damage zones at faults, and they show the difficulties associated with S-wave methods in areas with caliche. Combining all of the geophysical data from the Area 7 stu...

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GIS Surface effects archive of underground nuclear detonations conducted at Yucca Flat and Pahute Mesa, Nevada Test Site, Nevada

Cited by 5 publications

References 2 publications

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

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

Conceptualization of the predevelopment groundwater flow system and transient water-level responses in Yucca Flat, Nevada National Security Site, Nevada

Electrical Resistivity and Seismic Surveys at the Nevada Test Site, Nevada, April 2007

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