YELLOWSTONE LAKE SEICHE: ITS CAUSES AND IMPLICATIONS REGARDING THE CALDERA

It has recently been verified that signals detected on strainmeters throughout the Yellowstone National Park are caused by seiche waves in Yellowstone Lake. A seiche is a standing wave in an enclosed or partially enclosed body of water, leading to a harmonic, sloshing motion of the water. The purpose of this investigation is to determine whether both strong winds and changes in barometric changes are the main causes of the seiches. If wind was the only cause of the seiche, the signal would not be apparent in winter, when the lake is covered with ice. However, the signal is detected throughout the year, implying that there must be an additional cause for the signal, such as a change in barometric pressure. This is evaluated by comparing both barometric pressure data and wind speed data against strainmeter data using event detection of signal to noise ratios of data through the studied months. The strainmeter data has been detrended to account for the weight of snow, and the calibration pulses and Earth tides have been removed. Causes related to seismic activity have been ruled out. We compare wind data and barometric data with Yellowstone Lake strainmeter datasets from two separate times, winter 2011 and summer 2012, to see if both wind and barometric pressure are contributing to the seiche as expected. It is important to understand more about the seiche because, as a regularly occurring process, it can be incorporated to crustal models by using the lake’s mass and the known periodicity of its movements. The detection on strainmeters can be used to explain what lies under the lake, whether it is silicic magma or solid earth. Seiche signals detected on strainmeters over 20 km away from the lake indicate that it is not mostly solid earth under the lake. Also, the seiche oscillates much longer than other seiches typically do, supporting the hypothesis of an extensive magma chamber beneath the lake. Preliminary results using visual correlations between data are inconclusive- steady winds and changes in barometric pressure sometimes seem to influence seiching, but not always, indicating that another variable must be tested. More results will be available within coming months.