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Joint Inversion of Seismic and Acoustic Time Series for Time-Variable Source Parameters of the Buried Chemical Explosion at the Source Physics Experiment Phases Ii: Dry Alluvium Geology

Description: 

The estimation of seismic source mechanisms usually relies on wavefield inversion. In the typical inversion scheme, the input data consists solely of seismograms and the forward model only predicts wave propagation in the solid Earth. However, for local-scale analysis of buried chemical explosions, restricting the data type to seismic alone only may potentially miss a portion of the wavefield that carries additional information about the physics of the source. Specifically, the acoustic wavefield generated by a buried explosion can help to resolve source mechanisms that are associated with the explosion directly as well as ancillary explosion-induced phenomena such as surface deformation (spall).

To this end, we developed a linear wavefield inversion technique that uses a fully coupled, three-dimensional elastic-acoustic forward model to predict the seismoacoustic wavefield in both the solid Earth and the atmosphere simultaneously. Our inversion assumes the source can be approximated as a set of six independent, time variable, buried force couples (a time-variable moment tensor) as well as a spall term, which we approximate as a time-variable force applied to the Earth’s surface directly above the explosion. We use these seven source time functions (six from the buried source and one from the surface) to estimate the time-evolution of the source mechanism. Using synthetic data, we explore the ability of our method to resolve various source types as a function of time using various data time-series, seismic and acoustic, and spatial coverage. Finally, we use our method to analyze the seismic and acoustic data collected as part of the Source Physics Experiment Phase II Dry Alluvium Geology. We compare our results to those previously determined by inverting infrasonic time-series alone, where the source model consisted of a buried seismic source as well as a spall term.

SNL is managed and operated by NTESS under DOE NNSA contract DE-NA0003525.

Session: Exploiting Explosion Sources: Advancements in Seismic Source Physics [Poster]

Type: Poster

Date: 4/19/2023

Presentation Time: 08:00 AM (local time)

Presenting Author: Elizabeth M. Berg

Student Presenter: No

Invited Presentation: 

Authors