Faulting in the Yucca Mountain Area

David A. Ponce

FAULTING IN THE YUCCA MOUNTAIN AREA

INTRODUCTION--Why study faulting at Yucca Mountain?

Geophysical investigations of faulting are part of an effort to help geologically characterize a potential nuclear waste repository at Yucca Mountain. Whether or not faults exist and the length and the amount of offset along them are critical elements in determining the future earthquake hazard at Yucca Mountain.

Magnetic data along 29 profiles and gravity data along 13 profiles are reported along the central block of Yucca Mountain. The study area is about 130 km northwest of Las Vegas in the southwest quadrant of the Nevada Test Site (NTS) and is bounded by Yucca Wash to the north, Amargosa Valley to the south, Crater Flat to the west, and Jackass Flats to the east.

GEOPHYSICAL MAPS--
Facilitate Interpretation
(Click on image for a full-size).
Color contour map of ground magnetic observations along central block traverses. Red colors, magnetic highs; blue colors, magnetic lows; gray lines, mapped faults.

RESULTS

Geophsical data reveal that Midway Valley is charcterized by several known and previously unknown faults, that the existence of the Yucca Wash fault is equivocal, and that the central part of the eastern flank of Yucca Mountain is characterized by numerous small-scale faulting. Gravity and magnetic data also reveal several large-amplitude anomalies that reflect larger-scale faulting along the margins of the central block.

ADDITIONAL INFORMATION

Ponce, D.A., 1996, Interpretive geophysical fault map across the central block of Yucca Mountain, Nevada: U.S. Geological Survey Open-File Report 96-285, 15 p., 4 sheets, scale: 1:24,000. PDF (4.3 Mb).

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