Modeling the propagation of volcanic infrasound with a 3‐D parabolic equation

Active volcanoes are significant sources of infrasound in the 1–4-Hz frequency band and are detectable at ranges of hundreds of kilometers. The propagation is affected by the atmospheric temperature, wind, and attenuation profiles, which are range and time dependent. In this paper, a 3-D atmospheric parabolic equation method that accurately incorporates the effects of wind is applied to modeling volcanic infrasound propagation. A parabolic equation is derived using a narrow angle operator approximation in azimuth and a wide angle approximation in depth to account for wind-induced refraction that can trap or disperse sound energy, leading to large variations of propagation with wind conditions. The atmospheric specification for this model is derived from the attenuation coefficients of Sutherland and Bass [J. Acoust. Soc. Am. 115, 1012–1032 (2004)] and the temperature/wind profiles from the Naval Research Laboratory Ground to Space model [J. Geophys. Res. 108, 4680–4691 (2003)], which provides global atmospheric profiles from the ground to 200 km altitude updated four times daily. Signal amplitude and direction of arrival estimates from the model are compared with measurements of volcanic infrasound at listening stations several hundred kilometers from the source. [Work supported by ONR.]