A Multidisciplinary Study of Shallow Water Microseisms in Yellowstone Lake

Date: 4/26/2019

Time: 06:00 PM

Room: Grand Ballroom

It has recently been observed that wind-driven waves on Yellowstone Lake generate significant microseismic energy at a period of ~1 s. This setting provides a near-ideal laboratory for probing the origin and propagation of shallow water microseisms because it is a relatively small, closed system with a regular diurnal pattern of microseism excitation. In the summer of 2018, we deployed a suite of instruments to monitor Yellowstone Lake microseisms. We deployed 40 5-Hz, three-component, Nodal seismometers around the perimeter of the lake and on three islands within the lake, 4 meteorological stations recording wind speed and direction, and two wave gauges recording wave speed and direction. This instrumentation complemented a separate, ongoing deployment of 10 lake-bottom seismometers (HD-YLAKE project) as well as the 7 permanent land-based seismometers that border on the lake and are part of the Yellowstone Seismic Network. Initial analyses of these datasets illustrate the tightly coupled nature of the processes that generate microseisms, starting with sustained winds that generate gravity waves on the lake surface. The amplitude and period of the lake waves increase until the fetch limited wavefield is saturated with a peak period of ~2 s. Contemporaneously, the amplitude and period of the lake-generated microseisms increase until reaching a peak period of ~1 s. The factor of two difference in peak period suggests that these are double frequency (secondary) microseisms, presumably generated by waves reflected off the shoreline and islands that interact with the primary wavefield.

Presenting Author: Keith D. Koper

Authors