Meteoric 10Be Reveals a Young, Active Accretionary Prism and Structurally Complex Décollement in the Vicinity of the 2011 Tohoku Earthquake Rupture

Christine Regalla, Paul Bierman, Dylan H. Rood

Research output: Contribution to journalArticlepeer-review

1 Scopus citations

Abstract

We present new meteoric 10Be concentration data from marine sediment cores recovered during Integrated Ocean Drilling Program Expedition 343 (JFAST) that help constrain the age, origin, and internal structure of the frontal prism at the Japan trench in the vicinity of the 2011 Tohoku-oki M9 earthquake rupture. 10Be sediment ages from the lower portion of the frontal prism range from ~0–10 Ma, with >60% of analyzed samples above the décollement yielding young ages <2 Ma. Repetition and inversion of high-over-low 10Be-concentration sediments indicate the presence of stratigraphic inversions that correspond to faulting and imbrication of late Miocene and Quaternary sediments. The density of faults inferred indicates that the frontal prism has a fault spacing on the order of 10 s of meters, and the identification of faults in the underthrust section suggests that the plate boundary décollement may be a zone with multiple slip surfaces. Comparison of 10Be concentrations in the frontal prism with those of the incoming and forearc slope sediments indicates that the majority of the prism is sourced from accretion of Pacific Plate sediments, rather than from reworked frontal prism or slope sediments. These data suggest that over at least the past ~1–2 Ma, the décollement preferentially has localized at or near the base of the incoming sediment section, with relatively efficient sediment accretion occurring even in the presence of subducted horst-and-graben topography.

Original languageEnglish (US)
Pages (from-to)4956-4971
Number of pages16
JournalGeochemistry, Geophysics, Geosystems
Volume20
Issue number11
DOIs
StatePublished - Nov 1 2019

Keywords

  • accretion
  • Japan trench
  • JFAST
  • meteoric Be
  • sediment subduction
  • Tohoku earthquake

ASJC Scopus subject areas

  • Geophysics
  • Geochemistry and Petrology

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