Electromagnetism for volcanology : history, significance, and prospect

Abstract

The present paper summarizes the history of applied electromagnetism for field volcanology in Japan and abroad. Achievements are presented especially on volcanomagnetic effect, resistivity structure and its time change, and volcanoelectric effect, with a special attention to the social requirements for eruption prediction. Japan has been one of the leading countries in this research field in the past half century. In particular, geomagnetic filed measurement is recently attracting a growing interest as a regular and standard item for volcano monitoring in this country. Other electric or electromagnetic methods, such as resistivity sounding or selfpotential, have also contributed to reveal shallow processes involving volcanic fluids beneath active volcanoes preceding, during, and after their eruptions. The author also proposes some future directions in developing measurement techniques to improve the spatial coverage, resolution, depth penetration as well as to seek for safer data acquisition.