The Meteorological Agency and its volcanic research panel plan to increase the number of volcanoes under surveillance from the current 86 to 108, sources said Friday.
An official decision on the increase will be made at a meeting Tuesday of the Coordination Committee for the Prediction of Volcanic Eruptions, they said.
The agency and the panel currently monitor 86 volcanoes, defining them as active due to their eruption histories over the past 2,000 years.
They will now define volcanoes that have erupted in the past 10,000 years as active, in line with common Western research practices, the sources said. The 22 new entries include Mount Yotei in Hokkaido, Mount Yufudake in Oita Prefecture and Toshima Island south of Tokyo.
The agency and panel plan to categorize the 108 volcanoes into three levels based on likelihood of eruption, they said.
The volcanoes with the highest risk include Mount Asama, which stretches over Gunma and Nagano prefectures, and Sakura Island in Kagoshima Prefecture. Mount Fuji will be included in the middle rank among other peaks that become active every 100 years or so, they said.