Photo/Illutration A shelter and radio communication system right below the top of Mount Ontake in central Japan this month (Masahiro Haba)

MATSUMOTO, Nagano Prefecture--A court has dismissed claims by bereaved families for damages over a volcanic eruption that left 63 hikers dead or missing in 2014, ruling that raising the alert level would not have prevented the tragedy.

But the Matsumoto branch of the Nagano District Court on July 13 acknowledged that the Japan Meteorological Agency’s decision to maintain the existing alert level without sufficiently examining data on Mount Ontake was unlawful.

Mount Ontake, which straddles the borders of Nagano and Gifu prefectures, erupted at 11:52 a.m. on Sept. 27, 2014, leaving 58 hikers dead and five still missing in the worst volcanic disaster to hit postwar Japan.

In the lawsuit, a group of plaintiffs sought a total of 376 million yen ($2.7 million) in compensation from the state and the Nagano prefectural government.

The plaintiffs contended that the agency’s decision to refrain from raising the alert level to 2 from 1 was inappropriate.

The volcanic alert level system, which works on a scale of 1 to 5, was introduced to the nation in 2007. It is designed to alert hikers and residents nearby of dangers based on the agency’s analysis of volcanic activities.

In the case of Mount Ontake, the alert level was kept at 1, which means normal, on the day of the eruption. Level 2 would restrict people from going near the crater.

The agency can raise the alert level for Mount Ontake if more than 50 volcanic temblors occur in a day and if a slight change in crustal movements is observed, among other potential signs indicating an eruption could happen.

The court pointed out that the agency has the discretion to issue an alert based on its staff’s expertise.

According to the ruling, the agency observed 52 volcanic temblors on Sept. 10 and 85 similar activities on Sept. 11.

But Presiding Judge Tsukasa Yamashiro noted in his ruling that the agency said in its literature that it would examine various data in its overall assessment prior to determining the alert level.

“The agency was not obliged to immediately elevate the alert level since the observation of more than 50 volcanic temblors a day was only a guide,” he said.

Two days before the eruption, on Sept. 25, some agency staff reported data showing a slight change in crustal movement that they suspected indicated a swelling of the mountain.

But the agency concluded after only 15-20 minutes of discussion that the data did not necessarily show a definite change in crustal movement.

On this action, the court ruled that it was illegal for the agency to defer a close examination of the observation data without carrying out more study and analysis.

But the court did not hold the state liable for damages on the grounds that even if the alert level had been raised to 2, it cannot be said that the hikers’ access to the crater would have been restricted before the mountain erupted and thus prevented the disaster.

The court also acknowledged that the agency’s handling of observation data was inappropriate.

Although volcanologists cautioned that the agency should be on the alert for low-frequency temblors as a possible sign of an imminent eruption, agency staff did not immediately report to their superior in charge of the matter, even though such temblors were recorded on Sept. 14, 16 and 24.

As for the Nagano prefectural government’s liability, the court dismissed the plaintiffs’ claim for compensation, saying prefectural officials were not responsible for maintaining and managing seismographs installed on the mountaintop and elsewhere for the agency.

Some of the seismographs were found to be not working due to old age before the eruption, and that they had been left in that condition for some time.

(This article was written by Okuto Ko, Takashi Endo, Masahiro Haba and Ryo Sasaki.)

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