Stealthy magma system behavior at Veniaminof Volcano, Alaska

Yuyu Li^1*Patricia M Gregg¹Zhong Lu²Jiahui Wang²

• ¹University of Illinois at Urbana-Champaign, Champaign, Illinois, United States
• ²Roy M. Huffington Department of Earth Sciences, Southern Methodist University, Dallas, North Carolina, United States

Although Veniaminof Volcano in Alaska experiences frequent eruptions and has eight permanent seismic stations, only 2 of the past 13 eruptions have had precursory signals that prompted a preeruption warning from the Alaska Volcano Observatory (AVO) since 1993. Seismic data from Venianimof indicates that most eruptions from 2000-2018 do not coincide with increased seismicity. Additionally, analyses of InSAR data available from 2015-2018 which covers the pre-, syn-, and post-eruption periods of the 2018 eruption do not show clear signs of deformation. The systemic lack of systematic precursory signals raises critical questions about why some volcanoes do not exhibit clear unrest prior to eruption. In this study, we utilize finite element, fluid injection models to investigate the magma system at Veniaminof and its ability to erupt with no observable earlywarning signals. Specifically, a series of numerical experiments are conducted to determine what model configurations lead to stealthy eruptionsi.e., producing ground deformation below the detection threshold for InSAR (< 10 mm) and developing no seismicity, yet resulting in tensile failure which will promote diking and eruption. Model results indicate that the primary control on whether eruption precursors from deformation and seismicity will be present are the rheology of the host rock and the magma flux, followed by the secondary control of the size of the magma chamber, and then its depth and shape. Volcanoes with long-lived thermally mature magma systems with moderate to small magma reservoirs are the most likely to exhibit stealthy behavior, with the smallest systems most likely to fail without producing a deformation signal. For stealthy volcanoes like Veniaminof and others in Alaska (e.g., Cleveland, Shishaldin, Pavlof) and around the world, understanding the underlying magma system dynamics through numerical modeling is critical for providing robust forecasts of future eruptive activity.