Temporal fluctuations of microseismic noise in Yellowstone's Upper Geyser Basin from a continuous gravity observation

Abstract

We find geodetically detectable events of significantly elevated microseismic noise in an eight day Scintrex CG‐3M continuous relative gravity occupation in the southern Upper Geyser Basin of the Yellowstone caldera. The noise is recorded as large excursions in the gravity data, with frequencies between 0.033 and 0.5 Hz, and durations of up to one hour. These microseismic excursions, with gravity root mean square [RMS] amplitudes of ∼50 to 350 μGal, are up to an order of magnitude larger than the observed background levels of noise. The noise is also recorded as elevated variability in the gravity RMS time‐series, with frequencies >0.033 Hz. We suggest that these periods of elevated and variable microseismicity reflect active hydrothermal processes in the geyser basin not captured previously.