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Using MOMA Broadband Array ScS‐S data to image smaller‐scale structures at the base of the mantle
Author(s) -
Wysession M. E.,
Fischer K. M.,
Aleqabi G. I.,
Shore P. J.,
Gurari I.
Publication year - 2001
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 - 10.1029/2000gl008485
Subject(s) - geology , mantle (geology) , core–mantle boundary , seismology , slab , geophysics , broadband , seismic tomography , amplitude , geodesy , physics , optics
ScS‐S residuals obtained at stations of the Missouri‐to‐Massachusetts (MOMA) temporary broadband seismic array are used to delineate variations in seismic velocity structure above the core‐mantle boundary (CMB) at scales smaller than observable with tomographic models. South American earthquakes recorded at MOMA reveal a slow‐velocity anomaly that is at least as small as the limit of the resolution of ScS waves, about 300 km across. This is modeled as being within a region of fast velocities in whole‐mantle models. The slow ScS‐S residuals correlate well with a peak in ScS/S relative amplitudes. The small region of slow shear velocity at the CMB could be a pocket of lower mantle rock trapped beneath the descending Farallon slab, or evidence of chemical boundary layer variations.