WIND-INDUCED MICROSEISMS FROM LAKE-ONTARIO

The characteristics of microseisms measured in four vaults of the Sout hern Ontario Seismic Network within 30 km of the shore of Lake Ontario are analysed It is shown that the rms values in the 1-3 Hz band are c oherent between the stations, indicating a common generative mechanism . A distinct onshore intermittent flux of Rayleigh-like wave energy wa s detected at a site near the shore. Microseismic energy in this band is distinctly correlated with the wind speed. The incremental microsei smic energy above an absolute minimum activity as a function of wind d irection, for a given fixed wind speed, correlates with the average fe tch of the wind over the lake, indicating that the source of microseis ms is the lake itself. The sensitivity to fetch effects is similar for both onshore and offshore stations indicating that shoaling is probab ly not a source. Niagara Falls, which also can have a wind-dependent f low from Lake Erie, causes a measurable effect to at least 25 km but d oes not significantly affect stations at a distance of 150 km.