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New tectonic plate found under Japanese capital

A Japanese researcher has identified a new tectonic plate lying beneath the Tokyo region, a discovery that could have major implications for the government's disaster prevention policies in the quake-prone capital, according to a news report yesterday.

Shinji Toda, a geology expert at a public research institute, says there is a 25km thick, 10,000km2 slab lying just below Tokyo Bay that was previously thought to be an extension of the Philippine Plate but is actually a separate tectonic plate, according to Kyodo News agency.

Toda, chief researcher at the National Institute of Advanced Industrial Science and Technology in Tsukuba city, studied data from 150,000 shallow earthquakes of at least magnitude-2 on the Richter scale that occurred between 1979 and last year. A three-dimensional distribution of their epicenters revealed the new plate, Kyodo said.

Phone calls to Toda's research center went unanswered yesterday.

Toda's findings would mean that a fourth plate is pressing up against a juncture, where the Philippine, Pacific and Eurasian plates already meet.

That discovery, if confirmed, may force the government to have to review its disaster prevention policies in the Japanese capital, which experts agree is overdue for a major earthquake.

Since the late 1970s, the government has strengthened its monitoring of seismic activity and regularly conducts drills and assessment studies in anticipation of Tokyo's next "big one."

In February, a Cabinet Office committee estimated that about 11,000 people would die and Japan as a whole would suffer about ?112 trillion (US$1.06 trillion) in economic damage if a major earthquake were to strike the capital, which is home to about 35 million people or about one-fourth of Japan's population.

Earlier this year, the world's largest reinsurance company, Munich Re, said Tokyo topped its world list of urban areas that could suffer catastrophic losses in lives and property from earthquakes, flooding, tsunamis or terrorism.
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