Evidence for a metastable olivine wedge inside the subducted Mariana slab

Satoshi Kaneshima, Taro Okamoto, Hiroshi Takenaka

Research output: Contribution to journalArticle

44 Citations (Scopus)

Abstract

An anomalous seismic velocity structure is revealed inside the subducted Pacific plate at northern Mariana near the deepest earthquake foci. We observe anomalous later phases in the P wave coda for a small cluster of deep earthquakes and an anomalous differential P wave slowness between a few pairs of the earthquakes belonging to the cluster. We interpret these observations with a 5% low velocity wedge which is nearly 25 km wide at the depth of 590 km and is truncated at 630 km. The wedge is bounded by two steeply dipping (60°-70°) transition layers with the thickness of about 4 km. The highly localized seismic anomaly inside the slab represents a wedge of metastable olivine (α) embedded in dry ringwoodite (γ). Deep earthquakes occur across only one of the boundaries of the metastable wedge, with some of them outside the wedge. The mechanism of deep earthquakes is discussed based on the spatial pattern of seismicity relative to the wedge.

Original languageEnglish
Pages (from-to)219-227
Number of pages9
JournalEarth and Planetary Science Letters
Volume258
Issue number1-2
DOIs
Publication statusPublished - Jun 15 2007

All Science Journal Classification (ASJC) codes

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

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