Anomalous low-velocity zone and linear alignment of seismicity along it in the subducted Pacific slab beneath Kanto, Japan: Reactivation of subducted fracture zone?

Junichi Nakajima, Akira Hasegawa

Research output: Contribution to journalArticlepeer-review

113 Citations (Scopus)

Abstract

A detailed investigation of the hypocenter distribution beneath Kanto, Japan, reveals a NW-SE-trending linear alignment of seismicity within the subducted Pacific slab. We estimate the 3D seismic velocity structure in the Pacific slab to understand the factors controlling the genesis of such intraslab earthquakes. A narrow low-velocity zone is imaged within the subducted slab over a length of ∼150 km, which partly penetrates into the mantle portion of the slab. The low-velocity zone correlates in space with the NW-SE-trending earthquake cluster. A reactivation of hydrated fracture zone formed prior to subduction is probably related to the low-velocity anomaly. Dehydration reactions of the hydrated oceanic mantle as well as the oceanic crust might lower the seismic velocity along the fossil fracture zone, accompanied by intraslab earthquakes. These observations support the hypothesis of dehydration embrittlement as the most viable mechanism for generating intraslab earthquakes.

Original languageEnglish
Article numberL16309
JournalGeophysical Research Letters
Volume33
Issue number16
DOIs
Publication statusPublished - 2006 Aug 1

ASJC Scopus subject areas

  • Geophysics
  • Earth and Planetary Sciences(all)

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