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AGU: Geophysical Research Letters

 

Keywords

  • lava dome
  • conduit shape
  • cosmic-ray muon

Index Terms

  • Exploration Geophysics: Instruments and techniques
  • Volcanology: Volcano monitoring
  • Volcanology: Remote sensing of volcanoes
  • Volcanology: Instruments and techniques

Abstract

GEOPHYSICAL RESEARCH LETTERS, VOL. 34, L22311, 5 PP., 2007
doi:10.1029/2007GL031389

Imaging the conduit size of the dome with cosmic-ray muons: The structure beneath Showa-Shinzan Lava Dome, Japan

H. K. M. Tanaka

Earthquake Research Institute, University of Tokyo, Tokyo, Japan

Physics Department, University of California, Riverside, California, USA

Atomic Physics Laboratory, RIKEN, Saitama, Japan

T. Nakano

Physics Department, Nagoya University, Nagoya, Aichi, Japan

S. Takahashi

Physics Department, Nagoya University, Nagoya, Aichi, Japan

J. Yoshida

Physics Department, Nagoya University, Nagoya, Aichi, Japan

H. Ohshima

Usu Volcanic Observatory, Hokkaido University, Sobetsu, Japan

T. Maekawa

Usu Volcanic Observatory, Hokkaido University, Sobetsu, Japan

H. Watanabe

Earthquake Research Institute, University of Tokyo, Tokyo, Japan

K. Niwa

Physics Department, Nagoya University, Nagoya, Aichi, Japan

We developed a radiographic technique to image a subsurface conduit shape using cosmic-ray muons. The test measurement was performed in Showa-Shinzan lava dome located in Hokkaido, Japan as an example. A muon detector with an area of 6000 cm2 was set up at the foot of the lava dome. Muon tracks recorded in nuclear emulsion films in the detector were analyzed to determine the level of energy absorption along different ray paths through subsurface beneath the lava dome. A typical angular resolution of the muon detector of 10 mrad corresponds to a spatial resolution of 10 m at a distance of 1 km, which is difficult to be addressed with seismological technique. We mapped differentially absorbed cosmic-ray muons, which depend upon the varying thickness and density beneath the dome. We successfully imaged the conduit shape and determined a conduit diameter of 102 ± 15 m, assuming the observed high absorption region beneath the dome is localized in the vent area.

Received 20 July 2007; accepted 15 October 2007; published 22 November 2007.

Citation: Tanaka, H. K. M., T. Nakano, S. Takahashi, J. Yoshida, H. Ohshima, T. Maekawa, H. Watanabe, and K. Niwa (2007), Imaging the conduit size of the dome with cosmic-ray muons: The structure beneath Showa-Shinzan Lava Dome, Japan, Geophys. Res. Lett., 34, L22311, doi:10.1029/2007GL031389.

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