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Understanding Vulcanian Eruptions Through Seismograms Obtained From Unsteady Conduit Flow Models

Mario Z. Ruiz 1, Fredric Lam 2, Eric M. Dunham 1, Qing Ji 1, Mario C. Ruiz 3, Patricia Mothes 3

  • Affiliations: 1Department of Geophysics, Stanford University, California, USA; 2Department of Earth Sciences, University of Oregon, Oregon, USA; 3Instituto Geofísico, Escuela Politécnica Nacional, Quito, Ecuador

  • Presentation type: Talk

  • Presentation time: Friday 14:30 - 14:45, Room S160

  • Programme No: 2.1.9

  • Theme 2 > Session 1

Abstract

Vulcanian eruptions are violent and explosive events caused by the destruction of a solid plug in the uppermost volcanic conduit. We introduce an inversion and modeling workflow applied to the powerful 14 July 2013 Tungurahua, Ecuador, vulcanian eruption to understand the initiation and evolution of the eruption. This is done by integrating conduit flow modeling with seismic data. We use QVolc (Lam, 2024), which solves the unsteady mass, momentum, and energy balance equations for a multi-phase magma with exsolution and fragmentation. Initial conditions are obtained in two steps. First, we invert seismograms for vertical seismic force, using 3D Green's functions with topography and heterogeneous properties, where we interpret the initial downward force as the loss of flow resistance from plug failure. Second, to obtain pre-eruptive conditions for the unsteady case, we solve the magmastatic problem with additional flow resistance from the plug and constrained by the inverted force. The added resistance provides overpressure that drives the eruption. The eruption simulation is initiated by eliminating the plug flow resistance, corresponding to plug failure. Next, we convert changes in shear stress and pressure on the conduit walls into seismic force and moment sources (Coppess et al., 2022), which are convolved with Green's functions to generate seismograms. The predicted displacements are compared with observations.  We adjust the plug's depth extent, flow resistance, and failure timescale to match the seismic data. We are extending our modeling above the vent to integrate infrasound data. This workflow provides insight into the physical processes driving Vulcanian eruptions.