NH43C-1897
Detection of Aeromagnetic Field Changes Using an Unmanned Autonomous Helicopter: Repeated Experiments at Tarumae Volcano (Japan)

Thursday, 17 December 2015
Poster Hall (Moscone South)
Takeshi Hashimoto, Institute of Seismology and Volcanology, Hokkaido University, Sapporo, Japan, Takao Koyama, Earthquake Research Institute, University of Tokyo, Tokyo, Japan, Takatoshi Yanagisawa, JAMSTEC Japan Agency for Marine-Earth Science and Technology, Kanagawa, Japan, Mitsuhiro Yoshimoto, Mount Fuji Research Institute, Fujiyoshida, Japan, Takao Ohminato, University of Tokyo, Bunkyo-ku, Japan and Takayuki Kaneko, Univ Tokyo, Tokyo, Japan
Abstract:
Volcanic eruptions often prohibit humans from approaching active craters. Meanwhile, it is important, especially at the initial stage of an eruption, to perform visual surveillance, geophysical/chemical measurements and material sampling in the vicinity of the craters. Besides scientific purposes, information from such surveys is helpful for the local government in deciding the response to volcanic unrest. We started airborne surveys using an unmanned helicopter on a trial basis in cooperation with the Hokkaido Regional Development Bureau. As a part of the project, we repeated aeromagnetic surveys over Mt. Tarumae (1,041m), one of the active volcanoes in northern Japan in 2011, 2012 and 2013.

Owing to its high accuracy of positioning control in the autonomous flight with the aid of GPS navigation and the fairly small magnetic field gradient in the air, temporal changes up to 30 nT were successfully detected through a direct comparison between separate surveys. The field changes in the air were mostly consistent with those on the ground surface, which suggested remagnetization due to cooling beneath the summit lava dome.

Through our three-year experiments, the unmanned helicopter was proved to be useful for aeromagnetic monitoring. Although the system still has some limitations in terms of maximum flight altitude and operational range from the base station, we emphasize the following three advantages of this technique. (1) Operation without exposing human to volcanic hazards. (2) Straightforward data processing procedure to obtain temporal magnetic field changes, which is especially important in an emergency response such as an ongoing unrest. (3) Great reduction of the cost to maintain ground-based monitoring stations for many years.

Acknowledgments: We express sincere thanks to Muroran and Sapporo Development and Construction Departments of the HRDB for the cooperation in the field experiments using their unmanned helicopter.

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