Imaging the Subsurface Plumbing Complex of Steamboat Geyser and Cistern Spring with Hydrothermal Tremor Migration Using Seismic Interferometry

Steamboat Geyser in Yellowstone National Park is the tallest active geyser on Earth—recorded eruption heights have exceeded 110 m since 1962 (Reed et al., 2021; White et al., 1988). In addition to the fascinating water discharge phase lasting less than an hour after the onset of an eruption, Steamboat earned its name from the roaring steam phase that could create a steam column hundreds-of-meters high above the ground and persist for days (White et al., 1988). Steamboat's major eruptions are episodic with only three major active phases recorded: in the 1960s, 1980s, and the ongoing eruptions since March 2018. The current active phase has had more than 130 eruptions to date that have been hypothesized to be associated with shallow magmatic volatile accumulation (Wicks et al., 2020) but the exact mechanism remains inconclusive (Reed et al., 2021). Sporadic eruptions did occur between active phases but most of these eruptions were not directly witnessed and only were accounted for after the fact. The recorded latest singular eruption before the current active phase was in 2015. Since 1966, Cistern Spring, located 100 m southwest of Steamboat, was observed to have its water level drop (by 5–7 m) and surface temperature decrease (about 20°) after major eruptions of Steamboat (White et al., 1975), suggesting these two features are interconnected. Such hydrologic connection persists in the current active phase; however, the exact location where Steamboat and Cistern are physically connected and how the interaction of the two might affect the eruption/recharge dynamics of Steamboat remain largely elusive.