Constraining properties of pyroclastic density currents with remote infrasound and seismic observations

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Pyroclastic density currents (PDCs) are hot mixtures of eruption-derived particles and gas that move laterally along the ground. PDCs are commonly generated by eruption column or lava dome collapse and are driven by negative buoyancy. Due to their mobility, rapid velocities, and high temperatures, PDCs are the most hazardous volcanic phenomena and are responsible for over 50% of volcanic-related fatalities. PDCs are also challenging to observe directly. In addition to their hazardous nature, PDCs occur infrequently and often are located in remote and inhospitable places. Furthermore, direct visual observations can usually only be made of the outer shell of the flow as the complex internal dynamics are obscured by visually opaque fluid. Therefore, most of our understanding about these multiphase, turbulent flows comes from geological observations of PDC deposits, laboratory studies and numerical models. This work extends knowledge of PDC dynamics by associating physical processes with seismic and infrasonic waves. Geophysical observations (infrasound and seismic) can be made at safe distances from PDC activity and can provide high-resolution information about PDC dynamics. This project also supports a postdoctoral scholar, who will engage in activities that bring STEM and natural hazard resources to schools in the Cascadia region.For this project we will be developing a quantitative framework to relate PDC properties and dynamics to geophysical observables. The researchers will perform 3D multiphase simulations of PDCs and compute the infrasound and seismic radiation. This will enable the investigators to directly compare the simulation outputs with field data, which will provide a way to validate and improve numerical models of PDC dynamics. The researchers will perform a sensitivity analysis to understand what properties the geophysical observables are sensitive to and will explore the geophysical signals of different physical processes that have been shown to be important to PDC dynamics, such entrainment and fluidization. The proposed work will increase fundamental scientific understanding about the processes governing PDCs and will aid in data interpretation and volcano monitoring efforts by developing quantitative links between geophysical observables and flow properties.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.