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Time-Variable Moment Tensor Inversion of Seismic and Seismoacoustic Data at the Source Physics Experiment Phase II: Dry Alluvium Geology

Description: 

Seismic source inversions that assume each component of the moment tensor has the same underlying source time function (STF) are often unable to accurately categorize the complexity of a source as it evolves in time. However, a full-waveform, time-variable moment tensor inversion, where each component of the moment tensor is independently allowed to vary in time, allows for a better understanding of the dynamics of a source. One such example of a complex source that is difficult to accurately represent with a conventional moment tensor would be an explosion, followed by slip on near-source joints. When a single STF is assumed for all components, this may instead be approximated as solely an explosion source or a double couple source, oversimplifying the source mechanisms involved. If instead a time-variable moment tensor inversion was used, these two mechanisms can be differentiated in time and space. In this study, we apply a time-variable moment tensor inversion to seismic and seismoacoustic data recorded as part of the Source Physics Experiment Phase II: Dry Alluvium Geology (DAG). We develop a joint inversion to invert the seismic and infrasound waveform data from the DAG-4 experiment for the six independent, time-variable components of the (subsurface seismic) moment tensor, as well as a vertical force function, a term that approximates the surface spall source. We plot the source mechanism as a function of time on the fundamental lune to better interpret how the DAG-4 source changes with time. Additionally, we compare the seismic and seismoacoustic moment tensor results, estimating the sensitivity of both the seismic and seismoacoustic inversion formulations to the moment tensor and vertical force function results to gain a better understanding of how the addition of infrasound data in a joint inversion framework can affect our interpretation of a source. SNL is managed and operated by NTESS under DOE NNSA contract DE-NA0003525.

Session: Advancements in Forensic Seismology and Explosion Monitoring [Poster Session]

Type: Poster

Date: 5/2/2024

Presentation Time: 08:00 AM (local time)

Presenting Author: Andréa

Student Presenter: No

Invited Presentation: 

Authors