WITHDRAWN Evaluating the Efficacy of Inverting Local-Scale, High Frequency Seismograms for Effective Source Mechanisms Using Various Source Assumptions
Description:
WITHDRAWN Seismic source parameters are usually estimated by fitting the observed data to a series of force couples scaled by a symmetric tensor. This type of analysis is quite successful for analyzing low frequency regional (0.05 – 0.1 Hz) and teleseismic (0.01 - 0.1Hz) wavefields, however it requires simplifying assumptions about the source. Specifically, the source is assumed to be a point in time and space, and the (assumed) source time function (STF) is assumed to be identical for all components of the moment tensor. For local-scale data (particularly high frequency data produced by buried explosions) that assumption may not be appropriate because the initial energy release from the explosion may produce secondary sources of seismic energy (e.g. explosion-induced fracturing). In these cases, the conventional inversion effectively averages all the source types and mechanisms into a single representation of the source, which in some cases can produce nonsensical and/or grossly inaccurate estimates of the seismic source parameters. For this work, we investigate the efficacy and pitfalls of various waveform inversion techniques with the goal of resolving the source mechanism of a small, buried, chemical explosion. The seismic data are collected on a network with stations no more than 100m from the surface-projection of the source, where the source is ~40m meters deep. We find that the conventional inversion techniques fail to describe the data to an acceptable level of fit. However, using a more complex inversion, where the STF is neither assumed nor restricted to be similar for all tensor components, we can better fit the data. The resulting time-variable moment tensor can be interpreted as a time-varying source mechanism. SNL is managed and operated by NTESS under DOE NNSA contract DE-NA0003525.
Session: Exploiting Explosion Sources: Advancements in Seismic Source Physics
Type: Oral
Date: 4/19/2023
Presentation Time: 02:30 PM (local time)
Presenting Author: Christian Poppeliers
Student Presenter: No
Invited Presentation:
Authors
Christian Poppeliers Presenting Author Corresponding Author cpoppel@sandia.gov Sandia National Laboratories |
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WITHDRAWN Evaluating the Efficacy of Inverting Local-Scale, High Frequency Seismograms for Effective Source Mechanisms Using Various Source Assumptions
Category
Exploiting Explosion Sources: Advancements in Seismic Source Physics