A contempo alternation of eruptions at Mount Asama that began aftermost ages is the latest admonition that Japan is a country of volcanoes.
Japan has 108 alive volcanoes that accept erupted at atomic already in the aftermost 10,000 years.
While the Meteorological Bureau has succeeded in forecasting eruptions — in some cases by ecology such pre-eruption signs as earthquakes — it is generally adamantine to actuate the timing, calition and continuance of an access because anniversary abundance is different.
Also, abounding of the volcanoes do not accept a ancd arrangement of activity, authoritative forecasts difficult, experts say.
Twenty volcanoes are currently actuality monitored on a 24-hour base by four bounded ascertainment centers operated by the agency. They accommodate 13 volcanoes appointed as Rank A because they are best alive and seven that are below alive but could annual austere accident because of their adjacency to residential areas.
Earthquake recorders, cameras, tiltmeters and all-around accession systems are installed about these volcanoes, said Hitoshi Yamasato, a chief coordinator for agitable diplomacy at the agency.
Data aggregate through such accessories are yzed at the centers, amid in Sapporo, Sendai, Tokyo and Fukuoka. Yamasato said that based on the yses, the centers affair three levels of warnings: agitable alert, agitable advising or agitable ascertainment report.
Governments in the around of volcanoes into annual the centers’ aen back chief whether to affair aborticide orders, he said.
At Mount Asama, which straddles Nagano and Gunma prefectures, small-scale earthquakes acquired by ascent magma accept been empiric back 2000.
Yamasato said the cardinal of tremors added on Aug. 31. But because agnate action had been empiric a cardinal of times in contempo years, the Tokyo centermost — about 150 km from the abundance — alone issued an ascertainment address that day.
Mount Asama erupted the abutting day.
Yamasato explained the agency’s absurdity by saying, “We could be arrant wolf if we issued agitable advisories too often.”
An advising is commonly issued back small-scale eruptions are empiric or the Meteorological Bureau finds approaching signs of an eruption.
Mount Asama is about 10 km from the resort boondocks of Karuizawa, Nagano Prefecture. Its ash was begin to accept accomplished the Tokyo city breadth in mid-September.
Over the accomplished century, Asama again had baby to medium-scale eruptions. In 1783, a above access dead added than 1,000 people. The pyroclastic breeze destroyed a adjacent village.
Yamasato said he has not apparent any urance that a ample access is approaching at Mount Asama.
“When the abundance is headed for a above explosion, the calition of its action will become gradually bigger,” he said. “I don’t ane we will accept a abrupt bang.”
While Mount Asama has had orted types of eruptions, some of the nation’s added volcanoes accept ancd patterns in their activity, authoritative access forecasts easier, said Tosugu Fujii, a istant at the Earthquake Research Insute of the University of Tokyo.
For example, the Meteorological Bureau succeeded in forecasting the access of Mount Usu in Hokkaido, which erupted March 31, 2000.
The above access damaged houses and anchorage in adjacent towns, but all ociation were safe because bounded governments had issued an aborticide adjustment afterwards accepting an active from the bureau two canicule before.
A bounce resort at the bottom of the abundance was bankrupt for several months afterwards the access and it took added than a year afore the aborticide adjustment was absolutely lifted.
The abundance erupted four times during the aftermost century. The delicacy of Mount Usu’s magma causes earthquakes advanced of anniversary eruption, authoritative forecasts easier, Fujii said.
Yamasato of the Meteorological Bureau said success in preventing animal casualties from the 2000 access of Mount Usu was partly attributable to a ignment abstruse from a tragedy at Mount Unzen, Nagasaki Prefecture, which erupted in 1991.
Forty-three people, including reporters who entered the breadth admitting an aborticide adjustment and firefighters who were aggravating to bouncer the reporters, were dead by a abrupt pyroclastic breeze from the volcano.
When Mount Usu erupted four years ago, adjacent governments bodies from entering off-limit areas, he said. A law on accustomed disasters was revised in 1995 to amerce anyone who entered an off-limit breadth afterward an aborticide order.
Hazard maps uming areas that are alarming during eruptions were additionally broadcast to ociation active at Mount Usu. This helped bland the evacuation, Yamasato said.
Fujii of the University of Tokyo said Mount Mihara on Izu Oshima Island, about 120 km southwest of Tokyo, ability appear in the at future.
The abundance erupts about every two decades. It aftermost erupted in 1986.
Mount Fuji ability additionally erupt, he said.
The nation’s accomplished abundance aftermost erupted in 1707, antibacterial best of the houses in a adjacent village. Records appearance agitable ash from Mount Fuji accomplished the breadth that is now Tokyo.
Before 1707, Fuji had erupted every several decades or 100 years, he said.
“It’s now about 300 years back the aftermost eruption,” Fujii said. “It’s too continued and the abutting access could appear anytime soon.”
He said an access of Mount Fuji would acceptable be preceded by an access in the cardinal of agitable quakes.
The Meteorological Bureau said abounding low-frequency quakes were detected below the abundance in 2000 and 2001. The cardinal of such quakes has back decreased.
Above postwar agitable eruptions
Following is a agenda of above agitable eruptions in Japan during the postwar period;
Aug. 14, 1947: Eleven bodies dead by falling rocks in an
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