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Earth, Planets and Space

, Volume 52, Issue 3, pp 143–154 | Cite as

A low velocity zone beneath the Hida Mountains derived from dense array observation and tomographic method

  • Makoto Matsubara
  • Naoshi Hirata
  • Shin’ichi Sakai
  • Ichiro Kawasaki
Open Access
Article

Abstract

Seismic waves suffer strong attenuation when propagating beneath the Hida Mountains in Central Honshu, Japan. In order to study this region in detail, we conducted three kinds of dense seismic array observations in and around the Hida Mountains in the summer of 1996. Picking P- and S-wave arrival time data from 54 events at 101 stations, 3175 P- and 2335 S-wave arrival time data were obtained for our tomographic study. Hypocenter locations and velocity structure were determined simultaneously. We assessed ray coverage and resolution of the velocity structure with checkerboard resolution tests. Ray paths for the model of the obtained velocity structure were examined in detail. There are two zones of low P-wave velocity, one at a depth of 4 km and the other at 15 km. The resolution is good at depths of 0–20 km for P-wave velocities and at depths of 0–15 km for S-wave velocities. A high VP/VS ratio (2.7) indicates that a partially melting rock exists beneath the Hida Mountains. The deep low velocity zone is located just above the upper/lower crustal boundary. These observations indicate that a magma reservoir exists in the upper crust beneath the Hida Mountains.

Keywords

Velocity Structure Grid Node Velocity Zone Earthquake Research Institute Travel Time Inversion 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© The Society of Geomagnetism and Earth, Planetary and Space Sciences (SGEPSS); The Seismological Society of Japan; The Volcanological Society of Japan; The Geodetic Society of Japan; The Japanese Society for Planetary Sciences. 2000

Authors and Affiliations

  • Makoto Matsubara
    • 1
  • Naoshi Hirata
    • 1
  • Shin’ichi Sakai
    • 1
  • Ichiro Kawasaki
    • 2
  1. 1.The Earthquake Research Institutethe University of TokyoBunkyo-ku, TokyoJapan
  2. 2.Toyama UniversityToyamaJapan

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