Soft Vibrations

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Science  05 Dec 2008:
Vol. 322, Issue 5907, pp. 1439
DOI: 10.1126/science.322.5907.1439a

Microseisms—the continuous, low-amplitude background vibrations in the solid Earth observed between earthquakes—are generated by ocean waves. Most microseism studies have concentrated on the vibrations transmitted as surface (S) waves, and have concluded that they originate in shallow coastal regions, but relatively little is known about microseisms that propagate as body (P) waves. Gerstoft et al. show that body waves measured at an array of sites in southern California are generated by distant storms in several distinct regions of the Northern and Southern Hemispheres, where the ocean is deep, and that they propagate through Earth's mantle and core. In addition to identifying source regions, these P waves can provide information about deep Earth structure along paths not usually sampled by global tomographic studies, because the earthquakes used in those analyses occur mostly along plate boundaries rather than in the open ocean. — HJS

Geophys. Res. Lett., 10.1029/2008GL036111 (2008).

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