P wave velocity structure in the Yucca Mountain, Nevada, region

Abstract

We have performed a crustal tomographic inversion using over 250,000 P arrival times from local earthquake sources and surface explosions in the Yucca Mountain, Nevada, region. Within the shallowest 2–3 km, topographic features tend to dominate the structure with high velocities imaged under Bare Mountain, the Funeral Mountains, and higher terrain to the east of Yucca Mountain and low velocities imaged under Crater Flat, Jackass Flat, the Amargosa Desert, and the caldera complexes. Imaged shallow velocities also show correlation with several known gravity and aeromagnetic anomalies. Below the basins (∼2–3 km depth), velocities vary between 5.5 and 6.5 km/s and lose many of the correlations seen in the shallowest layers; however, a few major structures, such as the Bare Mountain block, can be traced to at least 10 km depth. Additionally, we image structures that may be associated with the Wahmonie intrusion and pre‐Tertiary structural trends. Yucca Mountain itself is underlain by a high‐velocity upper crustal‐scale structure similar to other structures in the region such as Bare Mountain and may represent a Basin and Range style back‐tilted block, which may provide a structural explanation for Yucca Mountain's topographic expression. Additionally, the imaged, relatively low velocity basement under Crater Flat may provide a preferred conduit for magma intrusion into Crater Flat compared to Yucca Mountain, accounting for the lack of post‐Miocene volcanism observed at the mountain proper. We explore our tomographic results in the context of four major tectonic models that have been proposed for the Yucca Mountain region.