This CAREER proposal, co-funded by two Divisions in the Directorate of Geosciences (Earth Sciences and Atmospheric and Geospatial Sciences), is constructed around a plan for improving our knowledge of the source physics and atmospheric propagation effects that take place during volcanic eruptions while training students and international participants in these novel techniques. When volcanoes erupt they impinge upon the atmosphere and produce high-amplitude acoustic radiation. These volcano sounds are comprised of both high frequency (i.e., audible) and sub-sonic energy (i.e., low frequency, or infrasonic) components, which are directly relatable to the style and intensity of an eruption. Volcano acoustics is thus an important tool for both remotely tracking an eruption, which is vital to volcano monitoring endeavors, and for quantifying material fluxes, which is fundamentally important for studies of eruption dynamics. Moreover, because low frequency volcano sounds are often exceptionally intense they are generally detectable at distances ranging from tens to thousands of kilometers from the volcano. This allows for implementation of acoustic remote sensing networks for continuous surveillance of restless volcanoes and to probe the intervening atmosphere to track changeable winds and temperatures, which influence sound propagation.
Toward the improved understanding of eruption source physics and atmospheric propagation effects, PI Jeffrey Johnson and colleagues, along with a team of graduate students, will investigate volcano acoustic sources and the evolution of these signals as they are transmitted through the atmosphere. During proposed field work the research team will utilize dense networks of specialized broadband microphones to record the intense (and often continuous) acoustic signals produced by a spectrum of active volcanoes in Latin America. Together with conjoint optical, multi-spectral, and meteorological observations they will develop and test models of sound generation and atmospheric sound transmission. Acoustic source physics and propagation modeling have vital impacts for the burgeoning fields of atmospheric infrasound studies, which encompass disciplines as varied as nuclear test ban monitoring, explosion physics, urban noise pollution, microbarom climatology, atmospheric tomography, and geophysical investigation of phenomena such as thunder, bolides, and earthquakes. Broader impacts of the proposed volcano dynamical studies are also expected to lead to development of improved surveillance techniques for monitoring hazardous volcanoes, which can ultimately lead to better forecasting and mitigation of volcanic hazards. The international nature of this work will foster collaboration between scientists in the U.S., Mexico, Guatemala, Ecuador, and Chile.
