Opal-CT in chert beneath the toe of the Tohoku margin and its influence on the seismic aseismic transition in subduction zones

Jun Kameda, Atsushi Okamoto, Kiminori Sato, Koichiro Fujimoto, Asuka Yamaguchi, Gaku Kimura

Research output: Contribution to journalArticlepeer-review

2 Citations (Scopus)

Abstract

Thick accumulation of chert is a ubiquitous feature of old oceanic plates at convergent margins. In this study, we investigate chert fragments recovered by the Integrated Ocean Drilling Program expedition 343 at the Japan Trench where the 2011 Tohoku-Oki earthquake (Mw 9.0) occurred. This sample provides a unique opportunity to investigate in situ chert diagenesis at an active subduction margin and its influence on the kinematics of megathrust faulting. Our mineralogical analyses revealed that the chert is characterized by hydrous opal-CT and may therefore be highly deformable via pressure solution creep and readily accommodate shear strain between the converging plates at driving stresses of kilopascal order. As chert diagenesis advances, any further deformation requires stresses of >100 MPa, given the increasing transport distances for solutes as represented in cherts on land. The chert diagenesis is thus related to the mechanical transition from a weakly to strongly coupled plate interface at this margin.

Original languageEnglish
Pages (from-to)687-693
Number of pages7
JournalGeophysical Research Letters
Volume44
Issue number2
DOIs
Publication statusPublished - 2017 Jan 28

Keywords

  • asperity
  • chert
  • pressure solution creep

ASJC Scopus subject areas

  • Geophysics
  • Earth and Planetary Sciences(all)

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