Ocean wave sources of seismic noise | INSTITUT DE PHYSIQUE DU GLOBE DE PARIS

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  Ocean wave sources of seismic noise

Type de publication:

Journal Article

Source:

Journal of Geophysical Research-Oceans, Volume 116 (2011)

ISBN:

0148-0227

Numéro d'accès:

WOS:000294804000002

URL:

http://www.agu.org/pubs/crossref/2011/2011JC006952.shtml

Mots-clés:

UMR 7154 ; Sismologie ; directional wave spectra ; ocean waves ; seismic noise ; wave model

Résumé:

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.

Notes:

Times Cited: 10