Self-Potential Studies in Volcanic Areas (5)-Rishiri, Kusatsu-Shirane, and White Island-

• Main Authors: Takeshi Hashimoto, Tohru Mogi, Nishida Yasunori, Yasuo Ogawa, Naoto Ujihara, Mitsuhiro Oikawa, Masaki Saito, Shoei Mizuhashi, Tohru Wakabayashi, Ryokei Yoshimura, Anthony W. Hurst, Mitsuru Utsugi, Yoshikazu Tanaka
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Published: 2004
• Subjects: Main Crater; New Zealand; White Island
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.571.7571; http://uvo.sci.hokudai.ac.jp/~hasimoto/pdf/kiyou2003.pdf

We performed self-potential (SP) profiling or mapping in three volcanic fields, Rishiri (northern Hokkaido), Kusatsu-Shirane (central Honshu) and White Island (northern New Zealand). The SP profile on the western flank of Rishiri volcano showed a remarkable high in the summit side, which is similar to many other active volcanoes. Assuming a negative ζ-potential, it is likely that Rishiri volcano has a large hydrothermal circulation system, and therefore still has enough thermal energy to maintain this circulation. Kusatsu-Shirane volcano inversely showed a decreasing trend toward the summit. It is a contradictive result to the previous knowledge that a volcano with remarkable hydrothermal system shows negative SP on the top. We suspect that the low pH of ground water in this area makes ζ-potential null or positive, resulting in the reversed surface SP profile to ordinary cases. This idea should be examined by laboratory experiments in the future. In the Main Crater of White Island volcano, we found some small-scale anomalous patches associated with fumaroles and steaming ground. The small variability of SP is probably attributed to the very low resistivity of the ground. 1.