Seismotectonics beneath the tokyo metropolitan area, Japan: Effect of slab-slab contact and overlap on seismicity

Junichi Nakajima, Fuyuki Hirose, Akira Hasegawa

研究成果: Article査読

131 被引用数 (Scopus)


We first determine the configuration of the upper surface of the Pacific (PAC) slab beneath Kanto, Japan, from the distribution of interplate earthquakes relocated by an appropriate 1-D velocity model. Then, traveltime tomography is carried out to estimate three-dimensional seismic velocity structures around Kanto using 735,520 P wave and 444,049 S wave arrival times from 6508 local earthquakes. The obtained results suggest that the Philippine Sea (PHS) slab is subducting to depths of 130-140 km without a gap, even to the northwest of the Izu collision zone. We subsequently define the lateral extent of the contact zone between the bottom of the PHS slab and the upper surface of the PAC slab (PHS-PAC interface) and reveal that the slab contact zone underlies a wider area beneath Kanto in harmony with the Kanto plain. The downdip limit of interplate (thrust-type) earthquakes on the PAC slab is deepened by ∼30 km locally under the slab contact zone. This deepening is probably caused by a lower-temperature environment in the PAC slab, resulting from the overlap with the PHS slab subducting above and consequent thermal shielding by the PHS slab from the hot mantle wedge. We detect an extremely low-velocity anomaly in the easternmost portion of the PHS slab, which is probably attributable to serpentinization of mantle peridotite. Interplate earthquakes are almost absent along the PHS-PAC interface overlain by the serpentinized mantle in the PHS slab, suggesting that ductile deformation takes place along the interface because of low viscosity of the serpentine.

ジャーナルJournal of Geophysical Research: Solid Earth
出版ステータスPublished - 2009 8月 1

ASJC Scopus subject areas

  • 地球物理学
  • 地球化学および岩石学
  • 地球惑星科学(その他)
  • 宇宙惑星科学


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