Mechanisms of Near Field Non-Radial Motion From Underground Explosions in Various Geologies

Date: 4/24/2019

Time: 06:00 PM

Room: Grand Ballroom

The Source Physics Experiment (SPE) is being conducted at Nevada National Security Site (NNSS) site in granite (Phase I) and alluvium (Phase II). The goal of the SPE is to study the ground motion generated by underground chemical explosion sources in various geologies. Of particular interest is the understanding of mechanisms of shear wave generation observed during underground explosions, which may look like natural seismicity in the far field. Analysing the near field ground motion during Phase I, we have found that the joints present in granite create a source of shear motion which propagates into the far field. Recent experiments in alluvium geology (DAG-1 and DAG-2) showed that shear motion is generated in the near field despite the absence of joints. The signature of this motion is very different from the one observed in granite. We have conducted numerical simulations of the ground motion for underground explosions in both geologies using detailed geophysical site characterizations conducted for both Phase I and Phase II experiments. Results of these simulations suggest that there may be different mechanisms behind the shear motion generation in both cases.

This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

Presenting Author: Oleg Y. Vorobiev

Authors