Researcher Information

HASHIMOTO Takeshi

Professor

Subsurface imaging by the electromagnetic waves

Institute of Seismology and Volcanology, Subsurface Structure

basic_photo_1
ThemeStudies on the subsurface structure in seismic regions and volcanoes
FieldVolcanology, Geomagnetism and Geoelectricity
KeywordVolcano, Earthquakes, Geomagnetic observation, Electromagnetic survey, Eruption forecasting

Introduction of Research

For us, human being, underground is invisible, even it is 1cm below the ground surface. In costrast, we are able to see the galaxies of thousands lightyears away. This is bacause human eyes only sense the waveband of visible light. However, we can "see" the subsurface by means of the electromagnetic (EM) waves that have longer wavelengths than the visible light. One of the important research subjects of the Institute of Seismology and Volcanology is to elucidete the subsurface structure beneath Hokkaido, where plates are converging, and seismic and volcanic activities are high. Earthquakes do not occur uniformly on the Earth. Such localized distribution of earthquakes may be arisen from the subsurface inhomogeneity, as well as the mechanical force relevant. For instance, The 2018 Easten Iburi Earthquake took place in the SE side of the active fault system (Ishikari Toen Fault Zone) that is located at the eastern edge of the Ishikari Lowland. Based on the EM survey, which was performed by the ISV in the past (Fig.1, Ref.2), a deep part of the active fault system exhibited markedly low resistivity. Such knowledge on the subsurface structure may help us point out potentially hazardous areas due to seismicity in the future, altough the mechanism of such inhomogeneity is not yet fully understood.
study-image-0
An EW cross-section of the electrical resistivity in the Ishikari Lowland, Hokkaido (Ref.2, captions added on the figure in Yamaya et al., 2017).







study-image-1
A UV imager for visualizing the SO2 gas in volcanic plumes (Hashimoto et al., 2015).
study-image-2
Image processing to remove white smokes from pictures of a volcanic crater (Ref.1, Hashimoto et al., 2018).
study-image-3
A drone operating a gas measurement at Mt. Ontake volcano (Mori et al., 2016).

Representative Achievements

Volcanic smoke reduction in visible and thermal infrared imagery, T. Hashimoto, A. Terada, R. Tanaka, Earth Planets Space, 2018, 70:109.
Three‐Dimensional Electrical Resistivity Modeling to Elucidate the Crustal Magma Supply System Beneath Aso Caldera, Japan, M. Hata, N. Matsushima, S. Takakura, M. Utsugi, T. Hashimoto, M. Uyeshima, J. Geophys. Res. Solid Earth, 2018, 123 6334-6346.
Permeability-control on volcanic hydrothermal system: case study for Mt. Tokachidake, Japan, based on numerical simulation and field observation, R. Tanaka, T. Hashimoto, N. Matsushima, T. Ishido, Earth Planets Space, 2017, 69.
Aeromagnetic survey using an unmanned autonomous helicopter over Tarumae Volcano, northern Japan, T. Hashimoto, T. Koyama, T. Kaneko, T. Ohminato, T. Yanagisawa, M. Yoshimoto, E. Suzuki, Explor. Geophys., 2014, 45, 37-42.
The role of Thermal Viscous Remanent Magnetisation (TVRM) in magnetic changes associated with volcanic eruptions: insights from the 2000 eruption of Mt Usu, Japan, T. Hashimoto, T. Hurst, A. Suzuki, T. Mogi, Y. Yamaya and M. Tamura, J. Volcanol. Geotherm. Res., 2008, 176, 610-616.
basic_photo_2

Related industries

Social Infrastructure, Geopark, Mining resources, Energy
Academic degreeDr. Science
Self IntroductionIt is probably true in all research fields that you should closely and sincerely look at your data. In my personal opinion, it is also essential in geosciences to sense the object itself with your own eyes, ears, nose, tongue, skin, and mind. This action reminds you that any instrumental data is imperfect just in the same way as your physical perceptions are. At the same time, physical observation, in the literal meaning, can give you a joy of mindfulness. Many years ago, when I was a student, I was watching an erupting volcano from the crater edge. Then I felt myself as if I was evaporating into the surroundings from my skin.
Everything in the world is a once-in-a-life experience and never repeats. So, the Earth that you are going to see, and everything that happens on it, is what anyone has never seen before and is never seeing in the future. You see it now.
Academic background1991 Graduated. Faculty of Science, Kyoto University
1993 Master course finished. Graduate School of Science, Kyoto University
1996 Doctoral course finished. Graduate School of Science, Kyoto University
1996-2003 Assistant Prof., Kyoto University
2003-2015 Associate Prof., Hokkaido University
2015-Present Professor, Hokkaido University
Affiliated academic societyThe Volcanological Society of Japan
ProjectIntegrated Program for Next Generation Volcano Research and Human Resource Development
Earthquake and Volcano Hazards Observation and Research Program.
Room addressFaculty of Science Building 4 4-313