Basement structure of Hokkaido Komagatake Volcano, Japan, as revealed by artificial seismic survey

Shin'ya Onizawa, Hiromitsu Oshima, Hiroshi Aoyama, Tokumitsu Maekawa, Atsuo Suzuki, Hiroki Miyamachi, Tomoki Tsutsui, Takeshi Matsushima, Satoru Tanaka, Jun Oikawa, Norimichi Matsuwo, Keigo Yamamoto, Toru Shiga, Takehiko Mori

Research output: Contribution to journalArticlepeer-review


We investigate the basement structure of the Hokkaido Komagatake volcano, Japan, by an artificial seismic survey. By inverting first arrival time data, a three-dimensional P-wave velocity model down to 3 km b.s.l. is obtained. The resultant velocity model reasonably reflects regional geological features and is consistent with Bouguer anomalies. Around the Komagatake volcano, the velocity basement deepens to NNW on the whole, reflecting the deepening of the geological basement toward that direction. Higher velocities are observed in Oshima and Kameda Mountains where Neogene volcanic and sedimentary rocks are present. On the contrary, lower velocities are observed in lowlands surrounding the volcano, where Komagatake deposits and Quaternary sediments crop out. At the volcano, a prominent high velocity zone was detected from the surface down to a depth of 1.5 km b.s.l. Above the base, probably a contrast between the core part with higher proportion of massive lavas and intrusions and flank areas dominated by loose pyroclastic deposits caused the prominent high velocity. Below the base, it is thought that solidified intrusive bodies largely contribute to making the high velocity. Further, a high velocity elongates from Kameda Mountains to beneath the summit. This is due to a shallower of the volcano substratum.

Original languageEnglish
Pages (from-to)245-253
Number of pages9
JournalJournal of Volcanology and Geothermal Research
Issue number3-4
Publication statusPublished - Jun 10 2009

All Science Journal Classification (ASJC) codes

  • Geophysics
  • Geochemistry and Petrology


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