2024 Volume 133 Issue 2 Pages 91-100
The most serious situation from the viewpoint of disaster prevention in activity at Hakone volcano is a burst of volcanic gases and hot steam, as observed in 2001 and 2015. Using GNSS data and based on Mogi's model, it is found that the pressure sources of activity in 2001 and 2015 are relatively shallow compared to other sources of volcanic activity. Whether a pressure source is relatively shallow or not can be easily distinguished by noting changes in distance between GNSS observation sites at Odawara and Hakone. If the distance decreases, the pressure source is considered to be shallow. The extent of volcanic activity differs each time and only two cases of recent activity are known where dangerous surface phenomena are observed. Therefore, it cannot be said that volcanic activity with a shallow pressure source would always be hazardous and activity with a relatively deep source would not become dangerous. However, making use of empirical knowledge, it is believed to be meaningful to monitor volcanic activity more carefully when the pressure source is estimated to be relatively shallow.
