Variable seismic anisotropy across the Peruvian flat-slab subduction zone with implications for upper plate deformation

Cristobal Condori, George S. França, Hernando J. Tavera, Caroline M. Eakin, Colton Lynner, Susan L. Beck, Juan C. Villegas-Lanza

Research output: Contribution to journalArticlepeer-review

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.

Original languageEnglish (US)
Article number103053
JournalJournal of South American Earth Sciences
Volume106
DOIs
StatePublished - Mar 2021

Keywords

  • Flat-slab subduction
  • Northern Peru
  • Seismic anisotropy
  • Shear wave splitting

ASJC Scopus subject areas

  • Geology
  • Earth-Surface Processes

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