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On the composition of earth's short-period seismic noise field

Bulletin of the Seismological Society of America

By:
, , and
DOI: 10.1785/0120090120

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Abstract

In the classic microseismic band of 5-20 sec, seismic noise consists mainly of fundamental mode Rayleigh and Love waves; however, at shorter periods seismic noise also contains a significant amount of body-wave energy and higher mode surface waves. In this study we perform a global survey of Earth's short-period seismic noise field with the goal of quantifying the relative contributions of these propagation modes. We examined a year's worth of vertical component data from 18 seismic arrays of the International Monitoring System that were sited in a variety of geologic environments. The apertures of the arrays varied from 2 to 28 km, constraining the periods we analyzed to 0.25-2.5 sec. Using frequency-wavenumber analysis we identified the apparent velocity for each sample of noise and classified its mode of propagation. The dominant component was found to be Lg, occurring in about 50% of the noise windows. Because Lg does not propagate across ocean-continent boundaries, this energy is most likely created in shallow water areas near coastlines. The next most common component was P-wave energy, which accounted for about 28% of the noise windows. These were split between regional P waves (Pn=Pg at 6%), mantle bottoming P waves (14%), and core-sensitive waves (PKP at 8%). This energy is mostly generated in deep water away from coastlines, with a region of the North Pacific centered at 165?? W and 40?? N being especially prolific. The remainder of the energy arriving in the noise consisted of Rg waves (28%), a large fraction of which may have a cultural origin. Hence, in contrast to the classic micro-seismic band of 5-20 sec, at shorter periods fundamental mode Rayleigh waves are the least significant component.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
On the composition of earth's short-period seismic noise field
Series title:
Bulletin of the Seismological Society of America
DOI:
10.1785/0120090120
Volume
100
Issue:
2
Year Published:
2010
Language:
English
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Bulletin of the Seismological Society of America
First page:
606
Last page:
617
Number of Pages:
12