With sufficient instrumentation, infrasound can detect, locate, and characterize volcanic eruptions, even from thousands of kilometers away for large eruptions. My research focuses on improving eruption detection. A key problem in eruption detection in volcanic arcs is determining which volcano is erupting. Traditional bearing-estimation techniques require three or more element arrays to detect and estimate the back-azimuth to an infrasonic source. To overcome this requirement, I developed a robust seismo-acoustic technique to detect explosions and determine their bearing using ground-coupled airwaves, requiring only two local sensors: a 3-component seismometer and an infrasonic microphone (McKee et al., 2018). This is transformative because it expands a seismic station's capabilities simply by adding an infrasound sensor. I plan to expand my method in two ways: first, to test and apply it to remote infrasound, which involves path changes from direct arrivals to propagation through atmospheric waveguides, and second, to adapt it to locate sources.

Volcano infrasound is generated through the acceleration of a volume of air above a vent by the ejection of gas and often tephra. A key research area is linking infrasound volume-flow-rate estimates to mass eruption rate (MER; the mass and speed of ejected material), as it strongly controls ash plume dynamics and hazards. An infrasound wave passing across a mountain range will be heavily distorted and delayed when its wavelengths are at least an order of magnitude smaller than the mountain's length scales, resulting in a poorly characterized source. To assess the influence of topographic structures, I evaluated a local infrasound 3-D source location technique known as semblance. I found that the source location was off by hundreds of meters when wavelengths were comparable to, or even larger than, topographic features (McKee et al., 2014). Ultimately, I showed that determining accurate source locations requires assessing and removing topographic path effects and effects from local air temperature and wind (which strongly influence wave speed).