Variable seismic anisotropy across the Peruvian flat-slab subduction zone with implications for upper plate deformation
Abstract
We performed shear wave splitting analyses to investigate seismic anisotropy across the northern extent of the Peruvian flat-slab subduction region. We used core-mantle refracted SKS, SKKS and PKS phases from teleseismic events (88° > Δ < 150°) recorded at 45 broadband seismic stations from the Peruvian permanent and portable seismic networks as well as from, international networks (CTBTO, RSBR-Brazil, and RENSIG-Ecuador). The results reveal a complex anisotropy pattern with distinct variations in shear wave splitting along strike. In the northernmost region, the mean delay times range between 1.0 ± 0.2 s and 1.5 ± 0.2 s with fast directions predominantly oriented ENE-WSW approximately perpendicular to the trench, parallel with the motion of the subducting Nazca plate. In the central region of Peru, the predominant fast directions change to a SE-NW orientation that is oblique with the trench. These fast splitting directions are consistent with the pattern seen previously over the southern extent of the flat-slab and correlate well with the current geodetically derived motion of the overriding forearc, the Peruvian Sliver. These characteristics suggest a fundamental change in anisotropic behavior between the northern and central portions of the Peruvian flat-slab and imply that the upper plate deformation is a controlling factor.
Description
Date
2021-03
Keywords
Seismic anisotropy , Shear wave splitting , Flat-slab subduction , Northern Peru
Citation
Condori, C., França, G. S., Tavera, H. J., Eakin, C. M., Lynner, C., Beck, S. L., & Villegas-Lanza, J. C. (2021). Variable seismic anisotropy across the Peruvian flat-slab subduction zone with implications for upper plate deformation. Journal of South American Earth Sciences, 106, 103053. https://doi.org/10.1016/j.jsames.2020.103053
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Publisher
Elsevier