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Seismic anisotropy and slab dynamics from SKS splitting recorded in Colombia
Author(s) -
Porritt Robert W.,
Becker Thorsten W.,
Monsalve Gaspar
Publication year - 2014
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 - 10.1002/2014gl061958
Subject(s) - geology , subduction , seismology , trench , slab , induced seismicity , lithosphere , seismic anisotropy , anisotropy , shear wave splitting , volcano , volcanic arc , volcanism , slab window , bathymetry , geophysics , mantle (geology) , tectonics , oceanic crust , physics , oceanography , organic chemistry , layer (electronics) , quantum mechanics , chemistry
The Nazca, Caribbean, and South America plates meet in northwestern South America where the northern end of the Andean volcanic arc and Wadati‐Benioff zone seismicity indicate ongoing subduction. However, the termination of Quaternary volcanism at ~5.5°N and eastward offset in seismicity underneath Colombia suggest the presence of complex slab geometry. To help link geometry to dynamics, we analyze SKS splitting for 38 broadband stations of the Colombian national network. Measurements of fast polarization axes in western Colombia close to the trench show dominantly trench‐perpendicular orientations. Orientations measured at stations in the back arc, farther to the east, however, abruptly change to roughly trench parallel anisotropy. This may indicate along‐arc mantle flow, possibly related to the suggested “Caldas” slab tear, or a lithospheric signature, but smaller‐scale variations in anisotropy remain to be explained. Our observations are atypical globally and challenge our understanding of the complexities of subduction zone seismic anisotropy.