How ocean waves rock the Earth: two mechanisms explain microseisms with periods 3 to 300 s

Type Article
Date 2015-02
Language English
Author(s) Ardhuin FabriceORCID1, 2, Gualtieri Lucia3, Stutzmann Eleonore3
Affiliation(s) 1 : IFREMER, Lab Oceanog Spatiale, Brest, France.
2 : CNRS Ifremer UBO IRD, Lab Phys Oceans, Brest, France.
3 : PRES Sorbonne Paris Cite, Inst Phys Globe, Paris, France.
Source Geophysical Research Letters (0094-8276) (Amer Geophysical Union), 2015-02 , Vol. 42 , N. 3 , P. 765-772
DOI 10.1002/2014GL062782
WOS© Times Cited 149
Keyword(s) hum, infragravity waves, numerical model, microseisms
Abstract Microseismic activity, recorded everywhere on Earth, is largely due to ocean waves. Recent progress has clearly identified sources of microseisms in the most energetic band, with periods from 3 to 10 s. In contrast, the generation of longer-period microseisms has been strongly debated. Two mechanisms have been proposed to explain seismic wave generation: a primary mechanism, by which ocean waves propagating over bottom slopes generate seismic waves, and a secondary mechanism which relies on the nonlinear interaction of ocean waves. Here we show that the primary mechanism explains the average power, frequency distribution, and most of the variability in signals recorded by vertical seismometers, for seismic periods ranging from 13 to 300 s. The secondary mechanism only explains seismic motions with periods shorter than 13 s. Our results build on a quantitative numerical model that gives access to time-varying maps of seismic noise sources.
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