DATE, Hokkaido – Nearly a month since Mount Usu’s latest series of eruptions began, the southwestern Hokkaido mountain appears to have settled down, but experts warned Saturday that another large eruption could still be in the offing.
Volcanologists point out that history shows an eruption much bigger than those seen so far would be needed before volcanic activity completely subsides.
The 732-meter volcano erupted March 31 for the first time in nearly 23 years. About 8,000 residents of Date, Abuta and Sobetsu — all located at the foot of the mountain — are still subject to evacuation orders.
More than 50 craters have recently formed on the western face of Mount Nishi and at Mount Kompira, which make up the volcano.
Aerial observations of the craters Saturday confirmed that their activity has calmed from several weeks earlier.
“We are no longer seeing explosions with force that is in line with the size of the craters,” said an official of a local team of the Coordinating Committee for the Prediction of Volcanic Eruption.
In a similar finding, the surface of the ground at the western face of Mount Nishi appears to be settled. It rose about 30 meters in the eruption’s aftermath.
Hiromu Okada, who heads the committee’s local team of volcano experts, said these developments do not prove that the danger has already passed, as volcanic tremors were continuing at the mountain.
To accurately monitor the movement of magma at the mountain, the Meteorological Agency is preparing to install earthquake-measuring devices and global-positioning-system equipment at numerous locations.
The Construction Ministry plans to build a retarding basin near the upper reaches of the Itaya River, which runs through the outskirts of Abuta, to stem the river’s flow of earth and sand. The ministry also plans to use to unmanned, remote-controlled earth-moving equipment in particularly dangerous areas near the mountain. Meanwhile, some evacuated residents are preparing to move into temporary housing from early May. A briefing was held Saturday in Abuta, where more than 80 percent of the evacuees live, to explain the new housing units.
A stretch of the JR Muroran Line that had been closed due to the eruption resumed some services on Saturday. Three round-trip services a day will run between Toya and Nagawa stations.