1. Department of Natural History Sciences; Graduate School of Science; Hokkaido University; Sapporo; Japan
2. The Hokkaido University Museum; Hokkaido University; Sapporo; Japan
3. Insitute of Volcanology and Seismology; Russian Academy of Science; Kamchatka; Russia
4. Graduate School of Engineering and Resource Science; Akita University; Akita; Japan
5. Graduate School of Engineering; Hokkaido University; Sapporo; Japan