Guided wave observations and evidence for the low-velocity subducting crust beneath Hokkaido, northern Japan Geofluid processes in subduction zones and mantle dynamics

Takahiro Shiina, Junichi Nakajima, Genti Toyokuni, Toru Matsuzawa

研究成果: Article査読

5 被引用数 (Scopus)

抄録

At the western side of the Hidaka Mountain range in Hokkaido, we identify a clear later phase in seismograms for earthquakes occurring at the uppermost part of the Pacific slab beneath the eastern Hokkaido. The later phase is observed after P-wave arrivals and has a larger amplitude than the P wave. In this study, we investigate the origin of the later phase from seismic wave observations and two-dimensional numerical modeling of wave fields and interpret it as a guided P wave propagating in the low-velocity subducting crust of the Pacific plate. In addition, the results of our numerical modeling suggest that the low-velocity subducting crust is in contact with a low-velocity material beneath the Hidaka Mountain range. Based on our interpretation for the later phase, we estimate P-wave velocity in the subducting crust beneath the eastern part of Hokkaido by using the differences in the later phase travel times and obtain velocities of 6.8 to 7.5 km/s at depths of 50 to 80 km. The obtained P-wave velocity is lower than the expected value based on fully hydrated mid-ocean ridge basalt (MORB) materials, suggesting that hydrous minerals are hosted in the subducting crust and aqueous fluids may co-exist down to depths of at least 80 km.

本文言語English
論文番号69
ジャーナルearth, planets and space
66
1
DOI
出版ステータスPublished - 2014 12

ASJC Scopus subject areas

  • 地質学
  • 宇宙惑星科学

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