Bloomberg

Japan Must Stop Forecasting Quake Near Tokyo, Geller Says

April 14, 2011, 2:49 AM EDT

By Yuriy Humber

(Updates with government response in fifth paragraph.)

April 14 (Bloomberg) -- The Japanese government should stop trying to forecast when a major quake will hit near Tokyo because models behind the predictions are flawed, according to a geophysicist.

Since 1979, a year after Japan introduced a system that aims to predict big earthquakes three days prior to the event, temblors causing 10 or more mortalities have struck in areas assigned a low seismic risk rating, said Robert Geller, a professor of geophysics at the University of Tokyo.

“It is time to tell the public frankly that earthquakes cannot be predicted,” Geller said in a Nature magazine article published today. “We should instead tell the public and the government to ‘prepare for the unexpected’ and do our best to communicate both what we know and what we do not.”

A magnitude-9 quake and tsunami that hit Japan on March 11 left about 27,500 dead or missing and caused radiation leaks at a nuclear power plant in the country’s worst crisis since World War II. The quake shook areas where the probability for high seismic intensity forecast by Japan’s model was as low as 0.1 percent, compared with as high as 100 percent in places southwest of Tokyo, government data provided by Geller shows.

Japan may review its policy if scientific study supports a change, Chief Cabinet Secretary Yukio Edano said today, declining to comment on specific details.

Dismissing Evidence

“As a politician and not an expert, this is something I shouldn’t comment on as there are different views among specialists,” Edano told reporters today in Tokyo. “If necessary, we will review our earthquake policies based on expert opinion.”

Japan’s nuclear regulator and Tokyo Electric Power Co., the owner of the nuclear plant, dismissed evidence two years ago that a tsunami could overwhelm the plant’s defenses, according to minutes from a 2009 government committee meeting.

Japan has built its earthquake models on the assumption that various zones have “characteristic earthquakes,” allowing scientists to assign quake probabilities to regions, Geller said.

The locations of temblors that caused 10 or more deaths since 1979 are outside the main danger regions and “suggest the hazard maps and methods used to produce it are flawed and should be discarded,” Geller wrote in the article.

Extensive Monitoring

The only area that Japan monitors extensively and continuously is off the coast of Suruga Bay southwest of Tokyo, identified as the only place in the country where detection of movement in underlying tectonic plates allows a quake to be forecast, according to Japan’s education ministry.

The possible rupture in the zone southwest of Tokyo has already been named by the government as the “Tokai earthquake.”

“We’re not claiming we can predict all earthquakes, just the Tokai earthquake,” Sadayuki Kitagawa, the education ministry’s Director for Earthquake Investigation, said by phone in Tokyo today. The government will review its methods, Kitagawa said.

A 1979 law requires the Japan Meteorological Agency to monitor the area off the coast of Suruga Bay and report signs of an approaching quake to a panel of five geophysicists for review before passing the information to the prime minister.

The cabinet can declare a state of emergency, ceasing most activity on the adjacent coast, an important industrial area, according to Geller.

“Over the past 30 years or so, government spokesmen have used the term ‘Tokai earthquake’ so often that the public and news media have come to view it as a ‘real earthquake’ rather than merely an arbitrary scenario,” Geller said. “This misleads the public into believing that the clock is ticking down inexorably on a magnitude-8 earthquake that is certain to strike the Tokai district in the near future.”

--With assistance from Takashi Hirokawa and Sachiko Sakamaki in Tokyo. Editors: Aaron Sheldrick, Paul Gordon

To contact the reporter on this story: Yuriy Humber in Tokyo at yhumber@bloomberg.net

To contact the editor responsible for this story: Andrew Hobbs in Sydney at ahobbs4@bloomberg.net



「地震予知、即刻中止を」　東大教授、英誌に掲載

　「日本政府は不毛な地震予知を即刻やめるべき」などとする、ロバート・ゲラー東京大教授（地震学）の論文が14日付の英科学誌ネイチャー電子版に掲載された。

　「（常に）日本全土が地震の危険にさらされており、特定の地域のリスクを評価できない」とし、国民や政府に「想定外」に備えるよう求めた。

　「今こそ（政府は）地震を予知できないことを国民に率直に伝えるとき」とも提言しており、世界的な学術誌への掲載は地震多発国・日本の予知政策に影響を与える可能性もある。

　論文では、予知の根拠とされる地震の前兆現象について「近代的な測定技術では見つかっていない」と指摘し、「国内で1979年以降10人以上の死者が出た地震は、予知では確率が低いとされていた地域で発生」と分析。マグニチュード８クラスの東海・東南海・南海地震を想定した地震予知は、方法論に欠陥がある、としている。

　教授は「地震研究は官僚主導ではなく、科学的根拠に基づいて研究者主導で進められるべきだ」として、政府の地震予知政策の根拠法令となっている大規模地震対策特別措置法の廃止を求めた。

　また、福島第１原発事故についても「最大38メートルの津波が東北地方を襲ったとされる1896年の明治三陸地震は世界的によく知られている」とし、「当然、原発も対策されているべきで、『想定外』は論外だ」とした。

2011/04/14 02:02 【共同通信】