Three-dimensional crust and upper mantle structure at the Nevada test site

Journal Article · Thu Mar 10 00:00:00 EST 1983 · J. Geophys. Res.; (United States)

DOI:https://doi.org/10.1029/JB088iB03p02220· OSTI ID:6053180

Taylor, S R

The three-dimensional crust and upper mantle structure at the Nevada Test Site (NTS) is derived by combining teleseismic P wave travel time residuals with Pn source time terms. The NTS time terms and relative teleseismic residuals are calculated by treating the explosions as a network of 'receivers' which record 'shots' located at the surrounding stations. Utilization of the Pn time terms allows for better crustal resolution than is possible from teleseismic information alone. Average relative teleseismic P wave residuals show a consistent progression of positive (late arrivals) to negative residuals from east to west across the NTS. However, Pn time terms beneath Rainier Mesa are at least 0.3 and 0.5 s less than those beneath Pahute Mesa and Yucca Flat, respectively, indicating the presence of high-velocity crustal material or crustal thinning beneath Rainier Mesa. The time terms at Pahute Mesa are surprisingly uniform, and the largest time terms and residuals are observed in the northwest and southern parts of Yucca Flat. The Pn time terms show a slight correlation with the working-point velocity at the shot point for Pahute Mesa and Yucca Flat, indicating that part of the observed lateral variations are caused by shallow effects of the upper crust. Three-dimensional inversion of the travel time residuals suggests that Yucca Flat is characterized by low-velocity anomalies confined to the upper crust, Rainer Mesa by very high velocities in the upper and middle crust, and Pahute Mesa by a high-velocity anomaly extending through the crust and into the upper mantle. Relatively low velocities are observed in the lower crust beneath the Timber Mountain caldera south of Pahute Mesa with no expression in the upper mantle. These observed differences in velocity beneath the Tertiary Silent Canyon and Timber Mountain calderas may be related to their magma volume and mode of enrichment from a mantle-derived magma source.

• Research Organization: Lawrence Livermore National Laboratory, Livermore, California 94550
• OSTI ID: 6053180
• Journal Information: J. Geophys. Res.; (United States), Vol. 88:B3
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
45 MILITARY TECHNOLOGY, WEAPONRY, AND NATIONAL DEFENSE
NEVADA TEST SITE
CONTINENTAL CRUST
EARTH MANTLE
DATA ANALYSIS
LAYERS
MAGMA
NUCLEAR EXPLOSIONS
RESOLUTION
SEDIMENTS
SEISMIC P WAVES
THREE-DIMENSIONAL CALCULATIONS
WAVE PROPAGATION
EARTH CRUST
EXPLOSIONS
NATIONAL ORGANIZATIONS
SEISMIC WAVES
US DOE
US ORGANIZATIONS
580100* - Geology & Hydrology- (-1989)
580201 - Geophysics- Seismology & Tectonics- (1980-1989)
450200 - Military Technology
Weaponry
& National Defense- Nuclear Explosions & Explosives