Investigations of open magma system behavior at Veniaminof Volcano, Alaska

Mt. Venianimof, a caldera volcano, is one of the most active systems in the Aleutian arc. Volcanic seismicity, ground deformation, and volcanic gas are commonly used as precursory signals to provide early warning of volcanic activity and impending eruption. Although Veniaminof experiences frequent eruptions and currently has eight permanent seismic stations, only 2 of the past 13 eruptions have had precursory phases that prompted a pre-eruption warning from the Alaska Volcano Observatory (AVO; Cameron et al., Frontiers in Earth Sci., 2018). In this investigation, geophysical observations (seismicity and ground deformation) from Veniaminof Volcano are analyzed to better understand the evolution of the magma system leading up to and during its recent eruptions. Seismic data (from the USGS catalog; Power et al., USGS Series No. 2019-5037, 2019) show that most eruptions from 2000-2017 do not coincide with an increase in seismicity. On the other hand, several periods of increased seismicity are observed between 2008 and 2013, with no resulting eruptions. Persistent scatterer interferometry (PS-InSAR) and small baseline subset interferometry (SBAS-InSAR) are used to produce time-series of ground deformation from Sentinel-1 data, which is available from 2015 and covers the pre-, syn-, and post-eruption periods of the 2018 and 2020 eruptions. Some images from the summer of 2018 might indicate deformation prior to the 2018 eruption, which initiated in September, but the lowlarge signal to noise ratio, likely caused by atmospheric and topographic effects, makes it difficult to see a clear indication of volcanic deformation. There is no clear deformation signal prior to the February 2020 eruption event. Given the lack of precursory signals, it is hypothesized that Veniaminof is an open volcanic system. We utilize a finite element method (FEM) modeling, fluid injection approach (LeMével et al., JGR, 2016) to investigate the magma system at Veniaminof and its ability to erupt with no geophysical precursors. Specifically, a series of numerical experiments are conducted to determine what model configurations produce a ground deformation signal that remains below the detection threshold for InSAR (< 10 mm/yr) and no seismicity (as calculated by shear failure) while assuming a minimum flux of magma needed to produce the 2018 and 2022 eruptions. Initial results indicate that the resultant ground deformation is most sensitive to the depth and shape of the magma reservoir, with oblate, shallow reservoirs creating the greatest deformation signal. Additionally, deformation increases linearly with an increase in magma flux and magma flux has the greatest impact on whether or not shear failure is produced along the injection column or around the magma reservoir. We find that a prolate source inflating with a low magma flux may produce a "stealthy" eruption without clear seismic or deformation precursors.