Seismic structure of the northeastern Japan convergent margin: a synthesis

A. Hasegawa, S. Horiuchi, N. Umino

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156 Citations (Scopus)


Spatial distributions of the depths to the Conrad and the Moho discontinuities show that both discontinuities are deep in the middle of the land area and shallow toward the coastlines. The Pn velocity is as low as ~7.5 km/s beneath the land area, while that beneath the Japan Sea and the Pacific Ocean is 8.0-8.2 km/s. It changes abruptly at the transition zones, which are located along the coastlines. Precise structure and location of the subducted Pacific plate beneath the land area is inferred from converted or reflected seismic waves at the top or bottom of the plate. The Pacific plate subducts at an extremely low angle of ~5° for the first ~25-km depth, and then the dip steepens rather abruptly to ~30°. Tomographic inversions for seismic velocity structure delineate the inclined high-velocity Pacific plate with a thickness of 80-90 km and low-velocity zones in the crust and the mantle wedge beneath active volcanoes. Seismic attenuation tomography also shows similar zones of low-Q value beneath active volcanoes, although its spatial resolution is much lower. -from Authors

Original languageEnglish
Pages (from-to)22,295-22,311
JournalJournal of Geophysical Research
Issue numberB11
Publication statusPublished - 1994

ASJC Scopus subject areas

  • Geophysics
  • Forestry
  • Oceanography
  • Aquatic Science
  • Ecology
  • Water Science and Technology
  • Soil Science
  • Geochemistry and Petrology
  • Earth-Surface Processes
  • Atmospheric Science
  • Earth and Planetary Sciences (miscellaneous)
  • Space and Planetary Science
  • Palaeontology


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