Measurement of seismic P- and S-wave attenuation in volcanic tuff, Rainier Mesa Tunnels, Nevada Test Site

Abstract

Ground shock measurements resulting from a nuclear explosion in P tunnel at the Nevada Test Site indicate attenuation rates somewhat greater than observed for events detonated in other tunnels in the Rainier Mesa area. Because ground shock attenuation is a factor in containment mechanisms, prediction of this phenomenon is of some importance. Published studies indicate that the properties having most influence on ground shock attenuation gas voids and rock strength directly and indirectly affect elastic wave attenuation in a significant manner and to a greater extent than they do compressional-and shear-wave velocities. Therefore, attenuations of shear and compressional waves were measured at two sites in P tunnel and at one site in N tunnel to determine if differences in elastic wave attenuation exist between the two environments, and to evaluate the technique for its utility as a qualitative tool for estimating comparative ground-shock attenuation at proposed event sites.Spectral ratio, rise time, and time-domain amplitude techniques were used to reduce the data. The resulting values of Qp and Qs differ significantly between techniques. The data derived by the spectral ratio technique, considered most reliable, indicate greater attenuation at the P tunnel sites (Qp=18, Qs=18-23) than at N tunnel (Qp=23, Qs=35).Uncertainties in the effects of scattering and interference, particularly at the N tunnel site, indicate that additional measurements are necessary to support these results and to develop the best technique for determining Q in this environment.

A Hydrostratigraphic System for Modeling Groundwater Flow and Radionuclide Migration at the Corrective Action Unit Scale, Nevada Test Site and Surrounding Areas, Clark, Lincoln, and Nye Counties, Nevada

“…Many of the geophysical surveys were designed to address very specific and local geological issues related to a specific underground test and thus are of limited use in constructing CAUscale HFMs. These data include mainly tunnel and borehole velocity, gravity, and resistivity measurements (Carroll, 1986;1990;1994;Carroll and Kibler, 1983;Kososki et al, 1978;Hearst and Burkhard, 1989). More recent geophysical data were collected specifically for the UGTA 2-5 A.…”

“…Seismic refraction surveys were conducted in many drifts and boreholes in the Rainier Mesa and Shoshone Mountain tunnel complexes, primarily for determination of the velocity of the medium as input to ground shock calculations for underground explosions (Carroll, 1986;1994;Carroll and Kibler, 1983). Data from some of these surveys were also used to characterize regions of damage following underground tests (Carroll, 1983 (App, 1983;Burkhard, 1983).…”