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A Dataset That Samples the Atmosphere with Thousands of Explosion-Triggered Waveforms on Multiple Scales

In July of 2019, staff at the Oklahoma Geological Survey (OGS) documented an unusual observation in their field blog: seismic stations distributed over the state of Oklahoma (OK) had recorded sequences of repetitive, quasi-similar signals almost daily over the previous spring and summer months. These signals appeared after 16:00 UTC in the 5-15Hz band as wavetrains of short duration pulses (~1-3s widths) that were separated by 20s intervals and moved near acoustic propagation speeds over widespread regions of OK. The onset of a wavetrain at a particular station was generally marked by up to 26 distinct pulses, each separated in time by integer multiples of 20s, recorded for 1200s per day and for multiple months. These observations drew attention from multiple media platforms that include National Geographic and Scientific American. Our research found that these seismo-acoustic signals originated from demolition explosions (shots) that are regularly carried out by the Army at the McAlester Ammunition Plant (McAAP), in designated shot pits. The observation of these seismo-acoustic signals on sensors up to ~350km from McAAP, their report over media and concern from OK residents gave this so-called “acoustic anomaly” visibility to the public and media. We extend the initial cursory analysis of this acoustic anomaly from a public interest project to a scientific one and leverage 9 months of waveform observations on ≤ 115 seismic stations to perform an empirical perturbation analysis of atmospheric variability, over a range of spatial and temporal scales that span the troposphere to the thermosphere and that span seconds to seasons in time. We verify these observations against ground truth data documented in McAAP blast-logs to reveal a spatial-temporal variability in infrasonic return paths that is not captured by low resolution space-borne and weather balloon observations. Our assessment demonstrates that explosion-triggered pulses can resolve changes in the atmospheric state and winds with sub-minute fidelity.

Presenting Author: Joshua D. Carmichael

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