The Physical Basis of Lg Generation by Explosion Sources

Abstract

The goal of the project is to develop a quantitative predictive capability for explosion-generated Lg phases with a sound and unambiguous physical basis. The research program consists of a theoretical investigation of explosiongenerated Lg combined with an observational study. The specific question addressed by this research program is how the Lg phase is generated by underground nuclear explosions. This question is fundamental to how Lg phases are interpreted for use in explosion yield estimation and earthquake/explosion discrimination.

Microstructure analysis of spherical silicon solar cells with SnOx:Fy layers

“…The Si spheres were produced by powder melting method [15][16][17][18][19]. Non-doped bulks of Si powders were melted on template at 1450 °C, and naturally cooled.…”

Generation of High-Frequency P and S Wave Radiation from Underground Explosions

“…To this list of physical processes we propose to add secondary radiation generated during rock fracture in the source and to investigate its contribution using our model. Stevens et al [10] considered four candidate mechanisms for explosion generated Lg: 1) "Direct generation by the explosion source where the explosion is modeled as a point compressional source. "…”

“…This is approximately the strength of the secondary radiation calculated by Johnson and Sammis [7] for the NPE explosion. We propose to represent the nonspherical secondary radiation that is produced by our model as an equivalent CLVD, thereby interpreting the Stevens et al [10] result in terms of physical properties of the source medium that lead to asymmetry such as prestress, fracture anisotropy, and the depth dependence of confining stress, an effect we have not yet explored using our model.…”

Very High Performance Organic Photonic Devices

“…More specifically, it has been demonstrated (Bennett and Murphy, 1986;Taylor et al, 1988;Fisk et al, 2002) that the high frequency (6-8 Hz) spectral ratio of P (Pn or Pg) to S (Sn or Lg) provides the most robust separation of underground explosions and earthquakes for small seismic events recorded at regional distances. While the experimental evidence for the power of this discriminant that has now been accumulated is compelling, a problem remains in that there is currently no physical model of S wave generation by explosions that has been shown to be quantitatively consistent with the wide range of observations from explosion sources (Stevens et al, 2003). Consequently, extrapolation of existing regional P/S discrimination criteria to previously untested locations and source conditions is still subject to significant uncertainty.…”

“…Gupta et al, 1991Gupta et al, , 1997, or on direct generation of S and Rg waves by the non-isotropic components of the explosion source associated with spall and other nonlinear interactions of the primary explosion source with the overlying geology and free surface (e.g. Stevens et al, 1991Stevens et al, , 2003. Although significant theoretical and observational evidence has been marshalled to support the plausibility of both of these hypothetical sources of Lg, problems remain in that neither seems completely consistent with the wide range of Lg observational data which is currently available (Stevens et al, 2003).…”