Mount Usu mudslide warning issued


The Meteorological Agency on Tuesday warned of possible mudslides in areas around Mount Usu in southwestern Hokkaido as heavy rain is expected in the area from tonight through Thursday.

The agency said the mudslides around the volcano, which erupted Friday, could combine with volcanic ash and rocks loosened by seismic tremors.

The rain is expected to peak early Thursday and strong winds are also expected in the area. The winds may spread volcanic ash to wider areas, according to the agency.

Mount Usu continued emitting smoke from a number of volcanic fissures Tuesday as scientists again warned of the possibility of a violent eruption of the 732-meter-high mountain.

Hiromu Okada, a professor at Hokkaido University who heads a team of volcano experts surveying the mountain, said he had seen some houses damaged on the west face of the mountain, where faults have been observed, with the roofs leaning to one side.

“The possibility is strong that the formation of a lava dome is beginning,” Okada said.

After a volcano erupts, lava accumulating in its craters rises in the form of bulbous mounds called domes. If one explodes, it may release a pyroclastic flow of lava capable of incinerating whole towns in a matter of minutes.

Okada also told reporters that his team had discovered a new group of fault lines on the mountain. They are located several hundred meters north of another fault-line group discovered Monday, and their south-facing sides are depressed, he said.

Okada also reported that the faults discovered earlier appear to have grown in length and number, and that they have formed ditches that run north to south.

Similarly, scientists on Tuesday said that more craters on the mountain have been discovered and that the one on Mount Kompira is expanding.

In another finding, a Meteorological Agency official said the volcano appears to be entering a new stage of activity.

Measurements using the satellite-based global positioning system show the expansion and contraction of the earth’s crust is slowing at three points around the mountain.

“This is not so much that changes in the earth’s crust are settling down,” said Nobuo Hamada, who heads the agency’s Earthquake Prediction Division, “but rather that (the mountain) is heading toward the next stage of activity.”

About 4,500 local residents are still in evacuation shelters a full week after evacuation orders were first issued.

The authorities are now worried that a growing number of evacuees are beginning to suffer physical ailments and anxiety due to the prolonged crisis.

The volcano has paralyzed much of the region. Hokkaido Railway Co.’s Muroran Line has been closed for the past week, along with roads in the area, hampering the transport of basic goods.

However, the seismic tremors that had constantly been shaking the area a week ago had virtually ceased by early Tuesday, according to the Muroran Meteorological Observatory.

Authorities continued warning residents to be on alert for mudslides from Mount Usu, which still has a partial covering of snow.

However, the Ministry of Construction said the likelihood was low that the area would experience a large-scale mudslide, due to the small amount of volcanic ash on the mountain.