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

Research output: Contribution to journalArticlepeer-review

35 Citations (Scopus)


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.

Original languageEnglish
Pages (from-to)165-175
Number of pages11
JournalJournal of Volcanology and Geothermal Research
Issue number1-2
Publication statusPublished - Jan 1 2011
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Geophysics
  • Geochemistry and Petrology


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