Statistical characterization of atmospheric gravity waves by seismoacoustic observations

Abstract

AbstractWe examine acoustic‐to‐seismic coupled signals from ground‐truthed explosions in northern Utah that were observed by dense seismic networks. We simulate the observed signals using both classical ray theory and the parabolic equation method in order to better understand the influence of multiscale atmospheric structures on these signals. Atmospheric models correctly predict acoustic arrival times downwind of the source, but signals are commonly observed over a much larger area than predicted using baseline models including well within the shadow zones near the source. In order to properly explain the extent of the observed infrasound wavefield in range and azimuth, the results indicate that it is necessary to account for unresolved subgrid‐scale atmosphere structures. The results also clearly show the need to account for these structures in order to properly explain the observed wave signal duration. Without accounting for small‐scale atmospheric structure, the infrasound signals are predicted to last 5–10 s but are observed to last 30–80 s. Furthermore, the amplitudes of the coupled signals relative to background noise vary steadily with distance in a manner that matches the computed predictions. The results show that infrasound signals retain much information about the large‐ and small‐scale structures in the atmosphere through which they propagate suggesting that routine observations from dense regional seismic networks might also provide a novel means of atmospheric sounding.