Abstract

Microseisms were recorded by two separate arrays within 5 km of Norris Geyser basin, Yellowstone National Park, Wyoming. The data were analyzed using frequency-wavenumber (f-k) spectral techniques to investigate whether the microseisms are originating at the geyser basin and, if so, whether body waves emanating from a deep source could be distinguished from surface waves on the basis of phase velocity. Array aperture and seismometer spacing were systematically varied to examine a continuous wavenumber range of 0 to 100 cycles/km. Results from high-resolution f-k analysis show that the microseisms indeed originate at the geyser basin in the frequency range 1.5 to 6.3 Hz with phase velocities of 1.1 to 2.5 and 2.0 to 4.0 km/sec on arrays southwest and east of the geyser basin, respectively. Although we could not distinguish between surface waves and body waves originating near the surface solely on the basis of phase-velocity information, observed velocities clearly preclude the possibility that a deep hydrothermal system is responsible for body-wave microseisms in this area.

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