Funding for this research was provided by:
Ministry of Education, Culture, Sports, Science and Technology (Earthquake and Volcano Hazards Observation and Research Program, Integrated Program for Next Generation Volcano Research and Human Resource Development)
Received: 9 September 2020
Accepted: 24 December 2020
First Online: 11 January 2021
Ethics approval and consent to participate
: Not applicable.
: All authors have no competing interests.