Interferometric-Based Polarization Analysis: Implications of Geyser Architecture and Dynamics at Steamboat Geyser in Yellowstone National Park

Abstract:

An active geyser’s recharge and eruption are extremely dynamic. In response to the evolution of temperature and hydrostatic pressure within the plumbing, this two-phase-flow system experiences intensive steam bubble nucleation and collapse throughout the eruption cycle. Such steam-liquid phase transition generates seismic signals observed as hydrothermal tremor, thus the spatiotemporal pattern of its origin can depict the plumbing architecture and illuminate how the geyser operates internally. Steamboat (SB), the tallest active geyser on Earth, is thought to have a complex architecture and dynamics owing to the hydrologic interaction with the nearby Cistern Spring (CS), ~100 m SW of SB. To study the system, in 2019 we deployed a dense nodal array across the SB-CS area with an aperture of ~250 m, which recorded 6 eruption cycles with intervals ranging from 3 to 8 days. We observe distinct 1–5 Hz tremors emitted from SB and CS, which are persistent and show no isolated events and discernible arrivals. To simultaneously locate the tremors from both features, we perform multicomponent cross-correlation to isolate and enhance the coherent signals of interest with each station as the virtual source. We apply the same normalization to the 3-component data so that the particle motion excited by each virtual source is retained. We observe prevalent seismic P waves at receivers near the source, with complex wavefield transition and interference at distant receivers. Using the P wave linearity, we back project the polarized directions to constrain the 3D source location. The results provide the first 4D view of the tremor throughout the eruption cycles with hourly resolution. The plumbing geometry beneath SB is vertical and extends to at least ~120 m depth. The conduit beneath CS is vertical from the surface to ~65 m. The bottom of it is laterally connected to a large reservoir between ~80 and ~140 m depth through an oblique conduit. The center of the reservoir is offset 60 m SE of CS. Although we do not observe a clear physical connection between SB and CS via tremor locations, the evolution of the tremor depth indicates CS has an instant thermal but a delayed mass response to SB eruptions. Incorporating in situ pressure and temperature data, we will discuss the possible scenarios of the connection and the dynamic interaction between SB and CS.