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Abstract Broadband seismometers are sensitive to tilt as a consequence of their design. We used broadband data from Erebus volcano on Ross Island, Antarctica, and Augustine volcano in Lower Cook Inlet, Alaska, to make tilt measurements associated with individual volcanic explosions and investigate the near‐terminal magmatic system configuration of each volcano. At Erebus volcano we found no evidence of tilt associated with the classic Strombolian eruptions from the lava lake. Tilt has been observed preceding Strombolian eruptions at volcanoes. The lack of tilt at Erebus is evidence that its conduit system lacks sufficient viscous plugging or mechanical restrictions to generate slug‐transport or explosion‐related forces large enough to produce measurable tilt. At Augustine volcano we measured tilt changes associated with 13 events during the explosive phase of its 2006 eruption. We used the tilt changes to invert for a dual deformation source model of a depressurizing open conduit above a depressurizing prolate spheroid. This deflation source geometry is in agreement with an existing magmatic system model developed from petrologic, seismic, and Global Positioning System data. This further supports this model while highlighting the capabilities of seismometer ground tilt measurements as independent model constraints. 

We propose a state-of-the-art 5 to 8-station broadband network that includes robust low-noise shallow-drilled posthole broadband seismometer installations. We will require (Iridium) real-time telemetry, and free and open data streams, and power systems that allow close to year-round operation (year-round would be the goal). In the middle field season of this 4-year deployment, we would also like to conduct an experiment with the nodal 3-component instruments to investigate the properties and geometry of Erebus' near surface magma reservoir. Following rescoping, the project was amended to have all field work accomplished by PASSCAL Polar staff (with no field work funded for the PI team). Following further COVID-related supplemental 2020 iscussions, the end date was extended to 9/1/23 (4-years duration).