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Earth's free oscillations recorded by free‐fall OBS ocean‐bottom seismometers at the Lesser Antilles subduction zone
Author(s) -
Bécel A.,
Laigle M.,
Diaz J.,
Montagner J.P.,
Hirn A.
Publication year - 2011
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2011gl049533
Subject(s) - seismometer , geology , seismology , subduction , microseism , seafloor spreading , forearc , oceanography , geophysics , tectonics
Three unburied ocean bottom seismometers (OBS) equipped with Trillium 240 s broad‐band seismometers recorded spheroidal free oscillations of the Earth out to periods over 1000 s period, for the M = 8.1, April 1, 2007 Solomon Islands earthquake. In contrast to broadband observatories of the global network that operate in quiet continental locations, these instruments were dropped on the several‐km thick layer of sediments of the forearc and accretionary wedge of the Lesser Antilles subduction zone. Furthermore, a high ambient noise level due to the ocean surface infragravity waves is expected to cover the frequency band of Earth's normal modes band when recorded at these sites. In spite of these hostile environmental conditions, the frequency of clearly defined peaks of the Earth's normal modes were measured after the earthquake. This suggests that the recording of normal modes and long period waves can be extended to parts of the hitherto inaccessible ocean with currently available OBS technology.