Using MOMA broadband array ScS-S data to image smaller-scale structures atthe base of the mantle

Citation
Me. Wysession et al., Using MOMA broadband array ScS-S data to image smaller-scale structures atthe base of the mantle, GEOPHYS R L, 28(5), 2001, pp. 867-870
Citations number
22
Categorie Soggetti
Earth Sciences
Journal title
GEOPHYSICAL RESEARCH LETTERS
ISSN journal
00948276 → ACNP
Volume
28
Issue
5
Year of publication
2001
Pages
867 - 870
Database
ISI
SICI code
0094-8276(20010301)28:5<867:UMBASD>2.0.ZU;2-E
Abstract
ScS-S residuals obtained at stations of the Missouri-to-Massachusetts (MOMA ) temporary broadband seismic array are used to delineate variations in sei smic velocity structure above the core-mantle boundary (CMB) at scales smal ler than observable with tomographic models. South American earthquakes rec orded at MOMA reveal a slow-velocity anomaly that is at least as small as t he limit of the resolution of ScS waves, about 300 km across. This is model ed 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 amplitude s. 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.