Flow plane orientation in the upper mantle under the Western/Central United States from SKS shear-wave splitting observations

Author(s)
Eric Löberich, Götz Bokelmann
Abstract

The causes of seismic anisotropy are still under debate. In particular, it is important to understand the extent to which seismic anisotropy is due to more recent geodynamic activities in the asthenosphere, or to frozen-in deformation in the lithosphere. We show that these two endmember cases can in principle be distinguished using shear-wave splitting observations from SKS waves. This is illustrated by the simple example of pure olivine with horizontal a-axis, and differing orientations of the other two axes, namely, vertical b and vertical c. The azimuthal dependence of shear-wave splitting measurements is described by two parameters, which can provide additional information about subsurface deformation. In particular, the oscillation parameter d1 constrains the orientation of foliation. We demonstrate that shear-wave splitting in the Western and Central United States indeed shows the predicted azimuthal dependence, related to a mainly subhorizontally oriented flow plane of deformation in the upper mantle. This has important implications for asthenospheric flow.

Organisation(s)
Department of Meteorology and Geophysics
Journal
Geophysical Journal International
Volume
221
Pages
1125-1137
No. of pages
13
ISSN
0956-540X
Publication date
2020
Peer reviewed
Yes
Austrian Fields of Science 2012
105122 Seismic
Keywords
ASJC Scopus subject areas
Geochemistry and Petrology, Geophysics
Portal url
https://ucris.univie.ac.at/portal/en/publications/flow-plane-orientation-in-the-upper-mantle-under-the-westerncentral-united-states-from-sks-shearwave-splitting-observations(a7ce54cc-789d-4e71-8f26-710d170480a2).html