Seismic Source Inversions from Simulations of Underground Chemical Explosions in Cavities

Session: Explosion Seismology Advances [Poster]
Type: Poster
Date: 4/29/2020
Time: 08:00 AM
Room: Ballroom
Description: 

Chemical explosions within air create nonlinear shock waves that emanate from the source. In a cavity within the earth, these waves interact with the rock walls of the cavity, converting acoustic energy into seismic waves that then propagate within the solid earth. Eventually, the nonlinearities of the wave become negligible, and thus, standard far-field seismological techniques that assume linearity can be applied. Linear moment tensor inversion is a common tool used in seismology to understand the characteristics of the seismic source. In order to investigate the effects of cavities on linear moment tensor inversions, we utilize Sandia’s nonlinear algorithms to simulate the near-source, nonlinear region of the wavefield, and then couple this output as time-varying boundary conditions to a linear seismic code once the wavefield is within the linear regime. Although nonlinear algorithms can accurately simulate very near field ground motions, they are computationally expensive. On the other hand, linearized seismic wave propagation codes are computationally efficient and can accurately model the far-field linear wavefield, despite their simplification of the seismic source. We find the purely linear seismic moment tensor and source time functions that optimally fit the waveforms produced by a nonlinear source in a cavity. We will present results showing how cavities affect the recovered full waveform moment tensor inversions and will discuss how well the linear source models are able to reconstruct the waveforms from the nonlinear source.

Sandia National Laboratories is a multimission laboratory managed and operated by National Technology & Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525. SAND2020-0101 A

Presenting Author: Leiph A. Preston

Authors