Observation of the crustal movement by dense GPS network in the Miyake-jima

The Volcanic Observation Group of Miyake-jima Island (GPS Observation Group) has conducted GPS observation since the early morning of June 27 in response to the volcanic activity started with an earthquake swarm from June 26. Figure 1 shows our GPS network. We detected a significant change in crustal movement, which may be associated with the magma intrusion beneath the summit of Mt. Oyama on June 26 and 27, as shown in Figure 2. The key issues are as follows: 1) subsidence around the summit of Mt. Oyama; and 2) tensile opening on the west coast of the island. They can be explained by assuming the migration of magma beneath the summit. A part or all of magma might intrude toward the sea from the west coast of Miyakejima Island. Figure 3 shows the pattern of the contraction of the whole island; the contraction is dominantly taking place at the south of Mt. Oyama summit.

Fig. 1

Fig. 2

Fig. 3