Temporal changes in seismic velocity of the crust around Iwate volcano, Japan, as inferred from analyses of repeated active seismic experiment data from 1998 to 2003

Takeshi Nishimura, Satoru Tanaka, Teruo Yamawaki, Hidekazu Yamamoto, Takashi Sano, Minemori Sato, Hisashi Nakahara, Naoki Uchida, Shuichiro Hori, Haruo Sato

Research output: Contribution to journalArticlepeer-review

43 Citations (Scopus)

Abstract

We have examined temporal changes in seismic velocity of the crust through repeated active seismic experiments at Iwate volcano, Japan, where a significant volcanic activity and an M6.1 earthquake were observed in 1998. We apply a cross spectrum moving window technique to seismic data recorded at eight stations for the six explosions detonated from 1998 to 2003. The seismic velocity at the frequency range of 3-9 Hz decreased by about 1% during the three months including the occurrence of M6.1 earthquake. The seismic velocity gradually increased, and about one third of the decrease was recovered by 2002. Then, the seismic velocity decreased again in 2003. Spatio-temporal changes in the volumetric strains predicted from the M6.1 fault mechanism and the volcanic pressure sources are well correlated with the seismic velocity changes observed in 1998. However, the predicted stress fields are not completely matched with the observed velocity changes from 1998 to 2003. This inconsistency may be due to unknown regional tectonic stress field and/or localized stress fields induced by volcanic pressure sources. It should be noted that the observed velocity changes indicate frequency dependent characteristics although the mechanism is not yet understood.

Original languageEnglish
Pages (from-to)491-505
Number of pages15
Journalearth, planets and space
Volume57
Issue number6
DOIs
Publication statusPublished - 2005

Keywords

  • Active seismic experiment
  • Iwate vocano
  • Seismic velocity
  • Temporal changes

ASJC Scopus subject areas

  • Geology
  • Space and Planetary Science

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