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Anisotropy beneath 9 stations of the GEOSCOPE Broadband Network as deduced from shear‐wave splitting
Author(s) -
Ansel Valérie,
Nataf HenriClaude
Publication year - 1989
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/gl016i005p00409
Subject(s) - geology , seismogram , anisotropy , seismology , broadband , shear wave splitting , shear waves , polarization (electrochemistry) , shear (geology) , geophysics , physics , optics , petrology , chemistry
Polarization of SKS, ScS and S waves has been analyzed on digital 3‐components seismograms recorded at 9 stations of the recently installed GEOSCOPE broadband network. Splitting was observed for about 15 records, and is interpreted as being due to seismic anisotropy beneath the stations. From every record, it is possible to retrieve the fast direction at the station, and the time difference between the fast and slow polarization directions. Some 30 observations of quasi‐linear S‐pulses also help constrain the direction of fast velocity. Synthetic seismograms were built to test the validity of the method used to retrieve the parameters of anisotropy. Typical time‐differences are about 1 sec, corresponding, for example, to a 80 km‐thick zone of perfectly oriented pyrolite. The fast directions obtained at 3 continental stations in America (Westford, Santa Cruz, Heredia), could be related to plate tectonic processes. On the other hand, the fast directions found in 3 oceanic islands (Kipapa, Papete, La Réunion) differ strongly from the oceanic plate velocity direction there.