Seismic reflection evidence against a shallow detachment beneath Yucca Mountain, Nevada

In 1994, the U.S. Geological Survey (USGS) obtained intermediate-depth seismic reflection profiles across Crater Flat and Yucca Mountain, Nevada. Primary objectives of the seismic profiling were discrimination of the subsurface geometry of faults and imaging of the boundary between the pre-Tertiary sedimentary strata and the Miocene volcanic rocks of Yucca Mountain. Of major interest is the existence and geometry of a postulated west-dipping detachment fault beneath Yucca Mountain. Seismic profiling in the region is hindered by rugged topography; processing of the data is made difficult by complex velocity profiles resulting from sequences of welded and nonwelded volcanic units and their associated variations in physical properties. These reflection profiles provide critical input to efforts to evaluate tectonic models, probabilistic seismic hazards, and potential volcanic hazards near Yucca Mountain, site of investigations for a potential permanent repository for high-level nuclear waste