Exploring the Effects of Emplacement Conditions on Explosion P/S Ratios across Local to Regional Distances

Journal Article · Wed Dec 22 00:00:00 EST 2021 · Seismological Research Letters

DOI:https://doi.org/10.1785/0220210270· OSTI ID:1839876

Pyle, Moira L. ^[1]; Walter, William R. ^[1]

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1. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

High-frequency (~> 2 Hz) seismic P/S amplitude ratios are well-established as a discriminant to distinguish between natural earthquakes and underground explosions at regional distances (~200–1500 km). As research shifts toward identifying lower-yield events, work has begun to investigate the potential of this discriminant for use at local distances (<200 km), in which initial results raise questions about its effectiveness. Here, we utilize data from several chemical explosion experiment series at the Nevada National Security Site in southern Nevada in the United States to study explosion Pg/Lg ratios across the range of local to regional distances. Additionall, the experiments are conducted over differing emplacement conditions, with contrasting geologies and a variety of yields and depths of burial, including surface explosions. We first establish the similarities of Pg/Lg ratios from chemical explosions to those from historic nuclear tests and conclude that, as previous data have suggested, chemical explosion ratios are good proxies for nuclear tests. We then examine Pg/Lg ratios from the new experiment series as functions of distance, yield, depth of burial, and scaled depth of burial (SDOB). At far-local and regional distances, we observe consistently higher ratios from hard-rock explosions compared to ones in a weaker dry alluvium medium, consistent with prior regional distance results. No other trends with yield, depth of burial, or SDOB are strongly evident. Scatter in the observed ratios is very high, particularly at the shortest event-to-station distances, suggesting that small-scale path effects play a significant role. On average, the local distance explosion Pg/Lg ratios show remarkable consistency across all the variations in emplacement. Explosion source models will need to reproduce these results.

• Research Organization: Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)
• Sponsoring Organization: USDOE National Nuclear Security Administration (NNSA)
• Grant/Contract Number: AC52-07NA27344
• OSTI ID: 1839876
• Report Number(s): LLNL-JRNL--825777; 1039933
• Journal Information: Seismological Research Letters, Journal Name: Seismological Research Letters Vol. 93; ISSN 0895-0695
• Publisher: Seismological Society of America
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
Nevada nuclear explosions
P-waves
S-waves
alluvium
body waves
chemical explosions
clastic sediments
elastic waves
explosions
sediments
seismic waves
signal-to-noise ratio