SURFACE-WAVE POLARIZATION DATA AND GLOBAL ANISOTROPIC STRUCTURE

Authors
Citation
G. Laske et G. Masters, SURFACE-WAVE POLARIZATION DATA AND GLOBAL ANISOTROPIC STRUCTURE, Geophysical journal international, 132(3), 1998, pp. 508-520
Citations number
46
Categorie Soggetti
Geochemitry & Geophysics
ISSN journal
0956540X
Volume
132
Issue
3
Year of publication
1998
Pages
508 - 520
Database
ISI
SICI code
0956-540X(1998)132:3<508:SPDAGA>2.0.ZU;2-O
Abstract
In the past few years, seismic tomography has begun to provide detaile d images of seismic velocity in the Earth's interior which, for the fi rst time, give direct observational constraints on the mechanisms of h eat and mass transfer. The study of surface waves has led to quite det ailed maps of upper-mantle structure, and the current global models ag ree reasonably well down to wavelengths of approximately 2000 km. Usua lly, the models contain only elastic isotropic structure, which provid es an excellent ht to the data in most cases, For example, the varianc e reduction for minor and major are phase data in the frequency range 7-15 mHz is typically 65-92 per cent and the data are ht to within 1-2 standard deviations. The fit to great-circle phase data, which are no t subject to bias from unknown source or instrument effects, is even b etter. However, there is clear evidence for seismic anisotropy in vari ous places on the globe. This study demonstrates how much (or little) the fit to the data is improved by including anisotropy in the modelli ng process. It also illuminates some of the trade-offs between isotrop ic and anisotropic structure and gives an estimate of how much bias is introduced by neglecting anisotropy. Finally, ave show that the addit ion of polarization data has the potential for improving recovery of a nisotropic structure by diminishing the trade-offs between isotropic a nd anisotropic effects.