Ocean wave sources of seismic noise

Type Article
Date 2011-09
Language English
Author(s) Ardhuin FabriceORCID1, Stutzmann Eleonore2, Schimmel Martin3, Mangeney Anne2
Affiliation(s) 1 : Inst Francais Rech Exploitat Mer, Ctr Brest, Lab Oceanog Spatiale, F-29280 Plouzane, France Univ Paris 07, Inst Phys Globe Paris, Dept Sismol, F-75005 Paris, France
2 : Univ Paris 07, Inst Phys Globe Paris, Dept Sismol, F-75005 Paris, France
3 : CSIC, Inst Earth Sci Jaume Almera, Dept Struct & Dynam Earth, E-08028 Barcelona, Spain
Source Journal of Geophysical Research ( JGR ) - Oceans (0148-0227) (American Geophysical Union), 2011-09 , Vol. 116 , N. C09004 , P. 21 p.
DOI 10.1029/2011JC006952
WOS© Times Cited 204
Abstract Noise with periods 3 to 10 s, ubiquitous in seismic records, is expected to be mostly generated by pairs of ocean wave trains of opposing propagation directions with half the seismic frequency. Here we present the first comprehensive numerical model of microseismic generation by random ocean waves, including ocean wave reflections. Synthetic and observed seismic spectra are well correlated (r > 0.85). On the basis of the model results, noise generation events can be clustered in three broad classes: wind waves with a broad directional spectrum (class I), sea states with a significant contribution of coastal reflections (class II), and the interaction of two independent wave systems (class III). At seismic stations close to western coasts, noise generated by class II sources generally dominates, but it is intermittently outshined by the intense class III sources, limiting the reliability of seismic data as a proxy for storm climates. The modeled seismic noise critically depends on the damping of seismic waves. At some mid-ocean island stations, low seismic damping is necessary to reproduce the observed high level and smoothness of noise time series that result from a spatial integration of sources over thousands of kilometers. In contrast, some coastal stations are only sensitive to noise within a few hundreds of kilometers. This revelation of noise source patterns worldwide provides a wealth of information for seismic studies, wave climate applications, and new constraints on the possible directional distribution of wave energy.
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