Areas near Mount Zao rumbled with heightened seismic activity Tuesday after warnings that a potential eruption could threaten a popular Tohoku ski resort in the area were issued the previous day.
The volcano sits on the border of Miyagi and Yamagata prefectures, where 12 volcanic earthquakes had occurred by 11 a.m. Tuesday. The Meteorological Agency issued a volcanic warning the same day for areas around the crater — its first for the Zao area.
The agency warned the public to be on the lookout for falling rocks in areas within 1.2 km of the crater. The warning follows last year’s deadly eruption of Mount Ontake, on the border of Gifu and Nagano prefectures. Ontake, which erupted without warning, ejected rocks, boulders and other debris over a wide area and was the worst volcanic disaster in the postwar era.
Ash and pebbles could reach even farther if carried by the wind, the agency warned.
Following the warning, issued at 1:30 p.m. Monday, notices warning of other potential hazards were set up at key points in the agency’s area of responsibility, according to the Yamagata Prefectural Government. These included entrances to mountain trails, an observatory and a restaurant.
The agency advised nearby municipalities, including the towns of Zao, Shichikashuku and Kawasaki, all in Miyagi, and the cities of Yamagata and Kaminoyama in Yamagata, to raise alert levels in areas near the volcano.
With Ontake’s eruption still fresh in people’s minds, the latest warning quickly stoked fear in visitors, said a tourism association spokesman for the Zao ski and onsen resort.
“Okama is one of the key tourist spots in Zao,” he said, referring to the color-changing lake in Zao’s crater, “but people think the resort is already dangerous to enter, just because it has the same name as the volcano.”
The association has been fielding calls since the warning was issued, presumably from people who plan to visit the area, which also attracts many hikers, the spokesman said.
According to the Meteorological Agency, seismic activity has been growing since April 7, leading it to the belief that a small eruption might be near. This prompted it to raise the warning level from “normal” to “dangers in areas around the crater.”
As of Monday, volcanic quakes, or shallow seismic activity limited to the mountain and thought to originate from around the lake, continued to occur at a high frequency.
The quake tally this month had hit 182 as of 2 p.m. Monday, the agency said.
Japan has a total 110 active volcanoes.
The Coordinating Committee for the Prediction of Volcanic Eruptions, a panel administered by the agency, has identified 47 of these as requiring stepped-up monitoring for disaster prevention purposes.
Mount Zao is among them because it fits the pattern of having had periods of increased volcanic activity over the past 100 years.
The agency has four observation posts around the volcano. Cameras are set up at three of them, including the crater, while a seismograph and other measuring instruments have been installed at the fourth.
Mount Ontake erupted without warning on Sept. 27, shooting gas, rocks and ash into the air that killed 57 hikers. Six are still missing.
Ontake was also designated as a volcano requiring stepped-up monitoring because it has repeatedly erupted in the past few decades. Nevertheless, scientists failed to predict September’s eruption.
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