Computational modeling of volcanic eruptions and their seismic and infrasound radiation

Explosive volcanic eruptions similar to the 1980 Mount Saint Helens eruption can be monitored from a safe distance using seismometers, which measure shaking of the ground, and microphones, which measure sound waves in the atmosphere. The overall goal of this project is to develop connections between shaking, sound waves, what’s going on inside a volcano and its eruption plume, and why explosive eruptions occur. One possibility is that the magma conduit gets blocked, leading to pressure build-up which eventually destroys the blockage and causes an eruption. The project team will develop computer simulations that track magma as it travels through the volcanic conduit (in some cases, having to break through blockages), becomes fragmented, and is discharged into the atmosphere. These simulations can predict sound waves and ground shaking generated by the eruption. Predictions from the models will be compared with data from the 2013-2014 explosive eruptions of Tungurahua volcano in Ecuador, which are probably the most powerful explosive eruptions ever recorded. This research will be done in partnership with the Instituto Geofisico in Ecuador, who will be providing data and expert knowledge of the eruptions. The project will provide training for two to three PhD students and several undergraduates, and all of the computer programs the team develops to simulate the eruptions will be freely shared with other scientists. This project develops models of seismic and infrasound radiation from vulcanian eruptions. The goal is to use seismic and infrasound data to quantify the depth of fragmentation, the forces associated with plug rupture at the onset of eruptions, the mass eruption rate and total erupted mass, and the vertical momentum exchange between the solid Earth and atmosphere. These are useful to understand fundamental processes involved in vulcanian eruptions (e.g., under what conditions does a plug form and what causes it to rupture) and to provide inputs to eruption plume modeling. The project builds on previous NSF-supported work by the project team that produced the theory and workflow to compute synthetic seismograms from unsteady conduit flow models. The project team is continuing work on an open-source code that couples conduit flow to a compressible atmosphere, thereby also providing predictions of infrasound radiation and the flow structure of the eruptive jet and plume. This overall modeling framework will be used for generic studies to understand processes as well as to study actual eruptions for which seismic and infrasound data are available. For the latter, the project team has partnered with the Insituto Geofisico, Ecuador, to model the well-recorded 2013-2014 eruption of Tungurahua volcano. An additional component of the project is a study of seismic eruption tremor (incoherent waves in the ~1-10 Hz band), a ubiquitous characteristic of explosive eruptions that in some cases is correlated with plume height. The project team will explore multiple hypotheses for eruption tremor, including turbulence and particle-wall interactions above fragmentation, as well as unsteadiness of the fragmentation process as magma with variable viscosity and other properties passes through the fragmentation depth. Finally, the project team is incorporating water (including phase changes) into their multiphase modeling code, giving them the ability to study the interaction of magma with groundwater and seawater, including submarine eruptions. The open-source codes and modeling workflows will be provided to the community for use by volcano observatories and other researchers. 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.