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Origin and properties of hydrothermal tremor at Lone Star Geyser, Yellowstone National Park, USA

November 20, 2020

Geysers are rare geologic features that intermittently discharge liquid water and steam driven by heating and decompression boiling. The cause of variability in eruptive styles and the associated seismic signals are not well understood. Data collected from five broadband seismometers at Lone Star Geyser, Yellowstone National Park are used to determine the properties, location, and temporal patterns of hydrothermal tremor. The tremor is harmonic at some stages of the eruption cycle and is caused by near‐periodic repetition of discrete seismic events. Using the polarization of ground motion, we identify the location of tremor sources throughout several eruption cycles. During preplay episodes (smaller eruptions preceding the more vigorous major eruption), tremor occurs at depths of 7–10 m and is laterally offset from the geyser's cone by ~5 m. At the onset of the main eruption, tremor sources migrate laterally and become shallower. As the eruption progresses, tremor sources migrate along the same path but in the opposite direction, ending where preplay tremor originates. The upward and then downward migration of tremor sources during eruptions are consistent with warming of the conduit followed by evacuation of water during the main eruption. We identify systematic relations among the two types of preplays, discharge, and the main eruption. A point‐source moment tensor fit to low‐frequency waveforms of an individual tremor event using half‐space velocity models indicates average VS ≳ 0.8 km/s, source depths ~4–20 m, and moment tensors with primarily positive isotropic and compensated linear vector dipole moments.

Publication Year 2020
Title Origin and properties of hydrothermal tremor at Lone Star Geyser, Yellowstone National Park, USA
DOI 10.1029/2020JB019711
Authors Avinash Nayak, Michael Manga, Shaul Hurwitz, Atsuko Namiki, Phillip B. Dawson
Publication Type Article
Publication Subtype Journal Article
Series Title Journal of Geophysical Research
Index ID 70217038
Record Source USGS Publications Warehouse
USGS Organization Volcano Science Center