Experts lacked data to predict blast
TOKYO — The Japan Meteorological Agency failed to forecast Saturday’s eruption at Mount Ontake. The agency said it didn’t have sufficient data on past eruptions and could not read underground magma conditions accurately.
Sadayuki Kitagawa, head of the agency’s volcanology section, admitted failing to forecast the latest eruption.
“We can’t predict every eruption,” he said at a news conference held hours after Mount Ontake erupted for the first time in seven years.
To forecast a possible eruption of Mount Ontake, the agency had placed seismographs at 12 locations and devices to monitor crustal changes at five locations around the mountain. The agency monitored conditions on a round- theclock basis.
The number of tremors at Mount Ontake began rising at about noon on Sept. 10 and increased to a total of 85 on Sept. 11. But the agency kept the five- stage volcanic eruption warning at the lowest level because it couldn’t detect any crustal changes, an indicator of magma ascent. Agency officials never thought of raising the warning level because the number of tremors declined after Sept. 12.
However, volcanic tremors, which continued for more than one minute, began at 11: 41 a. m. on Saturday. At 11: 53 a. m., the agency confirmed volcanic smoke rising from the mountain. Members of the volcanology section gathered immediately and at 12: 36 p. m. the warning level was raised, which meant climbers are restricted from entering the mountain area.
Kitagawa said the agency failed to forecast the eruption because they have few experiences with eruptions at Mount Ontake.
Mount Ontake’s volcanic activity began 800,000 years ago. However, there had been no eruption in recorded history until the volcano erupted in 1979. After the 1979 eruption, the agency established the observation network with seismographs to monitor Mount Ontake on a 24- hour basis.
After that, Mount Ontake erupted in 1991 and 2007. The agency observed the increase of tremors and the expansion of the summit’s surface two months before the 2007 eruption. Like this time, however, the agency failed to forecast the eruption.