Topographic effects on infrasound propagation

• Published in: The Journal of the Acoustical Society of America 2012, Vol.131 (1), p.35-46
• Main Authors: McKenna, Mihan H., Gibson, Robert G., Walker, Bob E., McKenna, Jason, Winslow, Nathan W., Kofford, Aaron S.
• Format: Article
• Language: English
• Subjects: Acoustics; Aeroacoustics, atmospheric sound; Exact sciences and technology; Fundamental areas of phenomenology (including applications); Physics
• ISSN: 0001-4966; 1520-8524
• DOI: 10.1121/1.3664099

Infrasound data were collected using portable arrays in a region of variable terrain elevation to quantify the effects of topography on observed signal amplitude and waveform features at distances less than 25 km from partially contained explosive sources during the Frozen Rock Experiment (FRE) in 2006. Observed infrasound signals varied in amplitude and waveform complexity, indicating propagation effects that are due in part to repeated local maxima and minima in the topography on the scale of the dominant wavelengths of the observed data. Numerical simulations using an empirically derived pressure source function combining published FRE accelerometer data and historical data from Project ESSEX, a time-domain parabolic equation model that accounted for local terrain elevation through terrain-masking, and local meteorological atmospheric profiles were able to explain some but not all of the observed signal features. Specifically, the simulations matched the timing of the observed infrasound signals but underestimated the waveform amplitude observed behind terrain features, suggesting complex scattering and absorption of energy associated with variable topography influences infrasonic energy more than previously observed.