Storms of ultralong period (14-18 seconds) microseisms are shown to be concurrent with storms of the more familiar long period (7-9 seconds) microseisms, and to be related to the same meteorological disturbances. Data from Palisades, New York, were analyzed for two cases, one for a meteorological storm over the northeastern Pacific and one for a meteorological storm in the northwestern Atlantic. The conclusions are based on correlation of continuous spectral analyses of the concurrent microseism storms, and on ground particle motion studies.

The periods of the ultralong period microseisms at any given time are, within the precision of the measurements, twice the periods of the long period microseisms at that time.

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