Predicting volcanic eruptions remains a difficult challenge for the government


The central government has increased its staff and strengthened surveillance but still struggles to predict eruptions among Japan’s 111 active volcanoes and to alert people in dangerous areas.

A five-level Volcanic Alert System is used to inform the public and authorities about the status of volcanoes and what actions should be taken to mitigate disasters.

But alert levels are often raised too late.

Just before noon on October 20 last year, Takahiro Ohkura, a professor at Kyoto University’s Aso Volcanological Laboratory, was monitoring volcanic tremors with ground-based equipment when he spotted gray smoke about a kilometer away. thence rising into the blue sky of Mount Aso’s Nakadake No. 1 crater in Kumamoto prefecture.

“Oh, I knew it,” he said at the time.

Ohkura, 58, was on the lookout for a similar event as volcanic tremors had increased in amplitude following a small-scale eruption on October 14.

Other relevant institutions were also monitoring developments on the volcano.

The Japan Meteorological Agency, for example, raised the alert level to 2 on October 13 and released “volcanic activity details” on October 18 and 19. Such extraordinary advisories are issued when levels of volcanic activity increase.

The Aso Volcano Disaster Prevention Council, which organizes local governments and other entities in the region, has restricted entry to areas within 1 km of the crater. Heavy machinery used for engineering work has been removed near the crater.

A pyroclastic flow from the October 20 eruption, however, traveled 1.6 km, exceeding the initial projection of 1 km.

Five minutes after the eruption, the JMA raises the alert level to 3 and widens the prohibited zones to a radius of 2 km from the crater.

No one was injured, but 16 climbers were within 2 km of the crater at the time.

“We take this seriously,” Keita Torisu, senior coordinator for volcanic disaster mitigation at JMA Fukuoka regional headquarters, said of the delayed response at a press conference after the eruption.

Tourists visit a hill overlooking Mount Aso on March 16, a day after the volcanic alert level was lowered to low 1. (Shinichi Fujiwara)

Another volcano erupted before the alert level was raised, resulting in Japan’s deadliest post-war volcanic disaster.

Mount Ontakesan, which straddles Nagano and Gifu prefectures, erupted in 2014 as its summit and surrounding areas were crowded with climbers. Ash rained down the mountain, leaving 63 dead or missing.

The JMA had detected more than 50 volcanic earthquakes in advance but kept the alert level as low as 1.

The central government, learning from this eruption, has strengthened its volcano monitoring system and its information transmission capabilities.

Its continuous monitoring now covers 50 volcanoes, down from 47, while the alert level system’s operations cover 49 volcanoes, down from 30.

The JMA has increased the number of volcano staff at its headquarters and local meteorological offices from about 160 in 2014 to about 280.

Volcano status data and other information is sent by crater cameras and other devices to the four volcanic observation and warning centers in Tokyo, Sapporo, Sendai and Fukuoka for monitoring and analysis.

The JMA has still failed to predict the magnitude of the October 20 eruption of Mount Aso.

The agency has tentatively relaxed the criteria for raising the alert level specifically at Mount Aso.

“It remains difficult to predict the magnitude of an eruption,” said Ohkura, the professor who monitors the volcano. “It’s important to be on the lookout when you’ve caught harbingers and to properly convey alert level information to local communities and climbers.”

Precursors play a key role in predicting eruption scales.

“With the latest improvements in communications technology, it has now become possible, to a large extent, to capture precursors in remote locations,” a JMA official said. “But it still comes with unavoidable blind spots. Direct on-site monitoring remains the most reliable method.

The Asahi Shimbun

Universities have traditionally maintained observatories near major active volcanoes, with scientists assigned there to monitor the peaks.

These researchers have been compared to “home doctors” because they are there to detect signs of volcanic activity and to advise local governments on evacuation and other issues.

However, scientists have gradually withdrawn from observatories, mainly due to budget cuts after Japan’s national universities were reorganized into semi-public administrative bodies in 2004.

Education Ministry officials said that as of April, researchers were only permanently stationed at four observatories: Mount Aso; Mount Unzendake in Nagasaki Prefecture; Mount Sakurajima in Kagoshima Prefecture; and Mount Kusatsu-Shiranesan in Gunma Prefecture.

Hokkaido University’s Usu Volcano Observatory (UVO), established at Mount Usuzan in 1977, has remained unstaffed since a specially appointed associate professor retired in March last year.

The observatory’s permanent staff ended following budget cuts and a shortage of researchers, officials said.

In 2000, a full-time UVO researcher captured precursors to the Usuzan eruption and worked with the Sobetsu city government to evacuate over 10,000 people before the eruption.

No one was killed and the experiment is considered a successful case of volcanic disaster management.

The withdrawal of UVO personnel sent shockwaves among knowledgeable officials. The JMA, for its part, cannot afford to assign replacement personnel to Usuzan despite the general increase in staffing of the agency in charge of volcanoes.

The Sobetsu city government appointed two researchers who worked for UVO to serve as “expert disaster management advisors”, ensuring continued access to expert advice.

“Ideally, we want to have a (permanent) home doctor for Usuzan,” said Toshiya Tanabe, the 62-year-old mayor of Sobetsu who dealt with the 2000 volcano eruption as a government official. from the city.

“But there is a need to work with relevant experts and institutions to ensure that there is a volcanic disaster management setup that works within the current system.”

The Volcanic Alert System, which the JMA introduced in 2007, uses a five-level scale to show what actions need to be taken by disaster management institutions and residents, and what geographic areas are covered.

The system is operated on 49 of the 50 volcanoes under continuous monitoring. The only exception is at Iwoto Island, where there are no residents.

The Asahi Shmbun


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