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

Cristobal Condori Quispe, 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
Article number103053
JournalJournal of South American Earth Sciences
Volume106
DOIs
StatePublished - Mar 2021

Bibliographical note

Funding Information:
This study was supported by the Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior (CAPES - Brazil). We are thankful to J. Hu for providing the mantle flow model. We thank also the Peruvian (RENASIS) (https://portal.igp.gob.pe/red-sismica-nacional) from the Instituto Geof?sico del Per?, Brazilian (RSBR) (http://www.rsbr.gov.br/) and the Ecuadorian (EC) (https://www.igepn.edu.ec/red-nacional-de-sismografos) Seismographic Network for providing the seismological data. SplitLab is a free software package for teleseismic shear-wave splitting analysis developed by W?stefeld et al. (2008). A modified version of SplitLab by Robert Porritt was used for the analysis, and can be download here: https://robporritt.wordpress.com/software/. Maps were made with the GMT software (Wessel and Smith, 1998). GSF thanks CNPq for the PQ grants.

Funding Information:
This study was supported by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES - Brazil) . We are thankful to J. Hu for providing the mantle flow model. We thank also the Peruvian (RENASIS) ( https://portal.igp.gob.pe/red-sismica-nacional ) from the Instituto Geofísico del Perú, Brazilian (RSBR) ( http://www.rsbr.gov.br/ ) and the Ecuadorian (EC) ( https://www.igepn.edu.ec/red-nacional-de-sismografos ) Seismographic Network for providing the seismological data. SplitLab is a free software package for teleseismic shear-wave splitting analysis developed by Wüstefeld et al. (2008) . A modified version of SplitLab by Robert Porritt was used for the analysis, and can be download here: https://robporritt.wordpress.com/software/ . Maps were made with the GMT software ( Wessel and Smith, 1998 ). GSF thanks CNPq for the PQ grants.

Publisher Copyright:
© 2020 Elsevier Ltd

Keywords

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

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