Earth's Noise in the Range of Infragravity Sea Waves

摘要

It was shown experimentally that oscillations of the Earth's crust in the range of periods greater than 20 s are caused predominantly by infragravity sea waves (hereafter, IGWs) closely related to wind waves in the sea rather than pulsations of the atmospheric pressure. It has long been known that elastic waves with periods from 2 to 20 s propagating in the Earth's crust (later called microseisms) are related to progressive and standing gravity waves in the sea, which are generated by wind over marine basins [1]. The progressive and standing wind waves excite microseisms of the first and second type, respectively, when they interact with the seafloor. The period of microseisms of the second type is equal to the period of progressive wind waves, while the period of microseisms of the first type is equal to half of the period of progressive sea waves, because variations in the hydrostatic pressure in the standing sea wave changes twice during the period of a progressive sea wave [2].