Temporal changes in electrical resistivity at Sakurajima volcano from continuous magnetotelluric observations

Koki Aizawa, Wataru Kanda, Yasuo Ogawa, Masato Iguchi, Akihiko Yokoo, Hiroshi Yakiwara, Takayuki Sugano

研究成果: Contribution to journalArticle査読

24 被引用数 (Scopus)

抄録

Continuous magnetotelluric (MT) measurements were conducted from May 2008 to July 2009 at Sakurajima, one of the most active volcanoes in Japan. Two observation sites were established at locations 3.3. km east and 3 km west-northwest of the summit crater. At both observation sites, the high-quality component of the impedance tensor (Zyx) showed variations in apparent resistivity of approximately ±. 20% and phase change of ±. 2°, which continued for 20-180 days in the frequency range between 320 and 4. Hz. The start of the period of changes in apparent resistivity approximately coincided with the start of uplift in the direction of the summit crater, as observed by a tiltmeter, which is one of the most reliable pieces of equipment with which to detect magma intrusion beneath a volcano. A 2D inversion of MT impedance suggests that the resistivity change occurred at a depth around sea level. One of the possible implications of the present finding is that the degassed volatiles migrated not only vertically through the conduit but also laterally through a fracture network, mixing with shallow groundwater beneath sea level and thereby causing the observed resistivity change.

本文言語英語
ページ(範囲)165-175
ページ数11
ジャーナルJournal of Volcanology and Geothermal Research
199
1-2
DOI
出版ステータス出版済み - 1 1 2011
外部発表はい

All Science Journal Classification (ASJC) codes

  • Geophysics
  • Geochemistry and Petrology

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