Three-dimensional resistivity structure and magma plumbing system of the Kirishima Volcanoes as inferred from broadband magnetotelluric data

Koki Aizawa, Takao Koyama, Hideaki Hase, Makoto Uyeshima, Wataru Kanda, Mitsuru Utsugi, Ryokei Yoshimura, Yusuke Yamaya, Takeshi Hashimoto, Ken'Ichi Yamazaki, Shintaro Komatsu, Atsushi Watanabe, Koji Miyakawa, Yasuo Ogawa

Research output: Contribution to journalArticlepeer-review

43 Citations (Scopus)

Abstract

Broadband magnetotelluric (MT) measurements were conducted in 2010 and 2011 in the vicinity of Shinmoe-dake Volcano in the Kirishima volcano group, Japan, where sub-Plinian eruptions took place 3 times during 26-27 January 2011. By combining the new observations with previous MT data, it is found that an anomalous phase in excess of 90° is commonly observed in the northern sector of the Kirishima volcano group. Because the anomalous phase is not explained by 1-D or 2-D structure with isotropic resistivity media, 3-D inversions were performed. By applying small errors to the anomalous phase, we successfully estimated a 3-D resistivity structure that explains not only the normal data but also the anomalous phase data. The final model shows a vertical conductor that is located between a deep-seated conductive body (at a depth greater than 10 km) and a shallow conductive layer. By applying the findings of geophysical and petrological studies of the 2011 sub-Plinian eruptions, we infer that the subvertical conductor represents a zone of hydrothermal aqueous fluids at temperatures over 400°C, in which a magma pathway (interconnected melt) is partially and occasionally formed before magmatic eruptions. To the north of the deep conductor, earthquake swarms occurred from 1968 to 1969, suggesting that these earthquakes were caused by volcanic fluids.

Original languageEnglish
Pages (from-to)198-215
Number of pages18
JournalJournal of Geophysical Research: Solid Earth
Volume119
Issue number1
DOIs
Publication statusPublished - Jan 2014

All Science Journal Classification (ASJC) codes

  • Geophysics
  • Geochemistry and Petrology
  • Earth and Planetary Sciences (miscellaneous)
  • Space and Planetary Science

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