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When and why earthquakes trigger volcano and geyser eruptions remains unclear. In September 2022, Steamboat Geyser in Yellowstone, USA erupted 8.25 hours after a local M3.9 earthquake—an improbable coincidence based on the geyser’s eruption intervals. We leverage monitoring data from the surrounding geyser basin to determine if the earthquake triggered this eruption. We calculate a peak ground velocity of 1.2 cm s−1, which is the largest ground motion in the area since Steamboat reactivated in March 2018 and exceeds a threshold associated with past earthquake-triggered geyser eruptions in Yellowstone. Despite no changes in other surface hydrothermal activity, we found abrupt, short-lived shifts in ambient seismic noise amplitude and relative seismic velocity in narrow frequency bands related to the subsurface hydrothermal system. Our analysis indicates that Steamboat’s eruption was likely earthquake-triggered. The hours-long delay suggests that dynamic strains from seismic waves altered subsurface permeability and flow which enabled eruption. 

Abstract Doublet Pool is an active hydrothermal feature in Yellowstone National Park, USA. Approximately every half hour, it thumps for about 10 min due to bubbles collapsing at the base of the pool. To understand its thermodynamics and sensitivity to external factors, we performed a recurring multiple‐year passive seismic experiment. By linking recorded hydrothermal tremor with active thumping, we determine the onset and end of thumping, and the duration of silence between each thumping cycle. The silence interval decreased from around 30 min before November 2016 to around 13 min in September 2018. This change followed unusual thermal activity on the surrounding Geyser Hill. On a shorter time scale, wind‐driven evaporative cooling can lengthen the pre‐thumping silence interval. Based on energy conservation, we determine the heating rate and heat needed to initiate thumping to be 3–7 MW and ∼6 GJ, respectively. 

Abstract Steamboat Geyser in Yellowstone National Park is the tallest active geyser on Earth and is believed to have hydrologic connection to Cistern Spring, a hydrothermal pool ∼100 m southwest from the geyser vent. Despite broad scientific interest, rare episodic Steamboat eruptions have made it difficult to study its eruption dynamics and underground plumbing architecture. In response to the recent reactivation of Steamboat, which has produced more than 130 eruptions since March 2018, we deployed a dense seismic nodal array surrounding the enigmatic geyser in the summer of 2019. The array recorded abundant 1–5 Hz hydrothermal tremor originating from phase‐transition events within both Steamboat Geyser and Cistern Spring. To constrain the spatiotemporal distribution of the tremor sources, an interferometric‐based polarization analysis was developed. The observed tremor locations indicate that the conduit beneath Steamboat is vertical and extends down to ∼120 m depth and the plumbing of Cistern includes a shallow vertical conduit connecting with a deep, large, and laterally offset reservoir ∼60 m southeast of the surface pool. No direct connection between Steamboat and Cistern plumbing structures is found. The temporal variation of tremor combined within situtemperature and water depth measurements of Cistern reveals interaction between Steamboat and Cistern throughout the eruption/recharge cycles. The observed delayed responses of Cistern Spring in reaction to Steamboat eruptions and recharge suggest that the two plumbing structures may be connected through a fractured/porous medium instead of a direct open channel, consistent with our inferred plumbing structure.