Seismicity and state of stress in the central and southern Peruvian flat slab

Abhash Kumar, Lara S. Wagner, Susan Beck, Maureen D. Long, George Zandt, Bissett Young, Hernando Tavera, Estella Minaya

Research output: Contribution to journalArticle

16 Citations (Scopus)

Abstract

We have determined the Wadati-Benioff Zone seismicity and state of stress of the subducting Nazca slab beneath central and southern Peru using data from three recently deployed local seismic networks. Our relocated hypocenters are consistent with a flat slab geometry that is shallowest near the Nazca Ridge, and changes from steep to normal without tearing to the south. These locations also indicate numerous abrupt along-strike changes in seismicity, most notably an absence of seismicity along the projected location of subducting Nazca Ridge. This stands in stark contrast to the very high seismicity observed along the Juan Fernandez ridge beneath central Chile where, a similar flat slab geometry is observed. We interpret this as indicative of an absence of water in the mantle beneath the overthickened crust of the Nazca Ridge. This may provide important new constraints on the conditions required to produce intermediate depth seismicity. Our focal mechanisms and stress tensor inversions indicate dominantly down-dip extension, consistent with slab pull, with minor variations that are likely due to the variable slab geometry and stress from adjacent regions. We observe significantly greater variability in the P-axis orientations and maximum compressive stress directions. The along strike change in the orientation of maximum compressive stress is likely related to slab bending and unbending south of the Nazca Ridge.

Original languageEnglish (US)
Pages (from-to)71-80
Number of pages10
JournalEarth and Planetary Science Letters
Volume441
DOIs
StatePublished - May 1 2016

Fingerprint

seismicity
slab
slabs
ridges
Compressive stress
Geometry
geometry
Tensors
Benioff zone
Peru
tearing
Water
Chile
stress tensors
focal mechanism
dip
crusts
Earth mantle
tensors
inversions

Keywords

  • Flat slab
  • Nazca plate
  • Peru
  • Ridge buoyancy
  • Subduction geometry

ASJC Scopus subject areas

  • Geochemistry and Petrology
  • Geophysics
  • Earth and Planetary Sciences (miscellaneous)
  • Space and Planetary Science

Cite this

Seismicity and state of stress in the central and southern Peruvian flat slab. / Kumar, Abhash; Wagner, Lara S.; Beck, Susan; Long, Maureen D.; Zandt, George; Young, Bissett; Tavera, Hernando; Minaya, Estella.

In: Earth and Planetary Science Letters, Vol. 441, 01.05.2016, p. 71-80.

Research output: Contribution to journalArticle

Kumar, Abhash ; Wagner, Lara S. ; Beck, Susan ; Long, Maureen D. ; Zandt, George ; Young, Bissett ; Tavera, Hernando ; Minaya, Estella. / Seismicity and state of stress in the central and southern Peruvian flat slab. In: Earth and Planetary Science Letters. 2016 ; Vol. 441. pp. 71-80.
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