Discriminating Collapses From Explosions and Earthquakes
Description:
The sudden collapse of an underground cavity produces seismo-acoustic signals that may potentially identify these events and discriminate them from explosions and earthquakes. In moment tensor space these collapses are modeled as gravity driven closing cracks (e.g. Bowers and Walter, 2002; Chiang et al., 2018, Pasyanos et al., 2023). Using body waves, they may show less high frequency energy than nearby earthquakes and explosions (e.g., Walter et al., 2018). The creation of cavities with the potential for collapse can follow from mining activities or underground nuclear explosions, making understanding their source an important part of geophysical nuclear test monitoring. The conditions leading to a possible cavity collapse vary with geology and depth. During the historic period (prior to 1993) of nuclear testing at the former Nevada Test Site (now the Nevada National Security Site), collapses following explosions were common as documented in Springer et al. (2002). The collapse following the September 2017 North Korean announced nuclear test is the best documented case at other nuclear testing locations (e.g. Wang et al., 2018).
To better understand and identify collapses as a unique source type we are examining a set of several dozen collapses following nuclear tests from the 1970’s and 1980’s in southern Nevada. We are comparing these collapse events with recent chemical explosions that were part of the Source Physics Experiments (SPE - e.g., Snelson et al., 2013), which have helped provide insight into how explosions generate shear waves (e.g., Pyle and Walter, 2022). We want to understand how much of the relative lack of high frequency energy observed in the historic Nevada collapse ATRISCO and the 2017 North Korean collapse studied in Walter et al. (2018) is due the shallow nature of the collapse source occurring in lower velocity materials, and how much may be due to the gravity driven collapse mechanism itself. As part of this work, we also plan to compare the nuclear explosion cavity collapses with those from mining areas at different depths and geologies, in various parts of the world.
Session: Advancements in Forensic Seismology and Explosion Monitoring - I
Type: Oral
Date: 5/2/2024
Presentation Time: 08:30 AM (local time)
Presenting Author: William
Student Presenter: No
Invited Presentation:
Authors
William Walter Presenting Author Corresponding Author walter5@llnl.gov Lawrence Livermore National Laboratory |
Michael Pasyanos pasyanos1@llnl.gov Lawrence Livermore National Laboratory |
Gene Ichinose ichinose1@llnl.gov Lawrence Livermore National Laboratory |
Amanda Price price54@llnl.gov Lawrence Livermore National Laboratory |
Colin Pennington pennington6@llnl.gov Lawrence Livermore National Laboratory |
Rebecca Rodd rodd2@llnl.gov Lawrence Livermore National Laboratory |
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Discriminating Collapses From Explosions and Earthquakes
Category
Advancements in Forensic Seismology and Explosion Monitoring