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Friday September 1 12:13 AM ET
Island Chain Quakes Makes Tokyo Think of the Big 1

By Jon Herskovitz

MIYAKEJIMA, Japan (Reuters) - When Prime Minister Yoshiro Mori sounded the alarm for Japan's annual mock earthquake drill Friday, more people than usual may have been listening.

Some 70,000 quakes have rattled this Izu islands chain about 120 miles south of Tokyo this summer and a volcano on one of the isles has blown its top, prompting many to wonder if a major quake is about to strike the capital.

But despite some headline-grabbing predictions of doom in weekly Japanese tabloids and other media, the scientific consensus is that the latest seismic activity says little about whether Tokyo is poised for a rerun of the 1923 Great Kanto Earthquake which left 140,000 dead in its wake. Friday marks the anniversary of that temblor, one of the worst natural disasters to strike anywhere in the 20th century.

In an effort to be ready if it happens again, Mori and nearly six million Japanese, including his entire cabinet, were taking part in Friday's disaster drills.

Major media have quoted experts, some with impressive credentials, as saying the quakes jolting the Izu chain could signal a big one is heading for Tokyo.

``The quake on the Izu island of Niijima (on July 15) was a dangerous indicator of a Tokyo region quake,'' Kyodo news agency quoted Megumi Mizoue, head of a group of professors who advises the Meteorological Agency on earthquake prediction, as saying.

The mass circulation daily Mainichi Shimbun quoted Mizoue as saying the Izu quakes could trigger a Tokyo region earthquake ``if the epicenters shift in a northwesterly direction.''

No Scientific Link

Other experts, however, dismiss the notion of a scientific link between Izu's jolts and looming disaster in Tokyo.

``Personally I cannot imagine living in an area where more than 50 magnitude five earthquakes have occurred in less than six weeks,'' said Charles Watson, president of the Nevada-based Advanced Geologic Exploration.

``But there are no reasons to infer the Izu Island seismicity would be related to any major tectonic activity for Honshu,'' he said, referring to the main island of Japan. Tokyo University professor of geophysics Robert Geller said that the risk of a major Tokyo quake or a temblor of a scale that would cause serious damage is neither more or less likely than it was a few months ago.

``The mass media here have talked about the Tokai earthquake so much that this purely hypothetical scenario has somehow been assumed by the public and government to be a real and present danger, which is somehow much more likely to occur than other earthquakes,'' Geller said.

``This misconception is unfortunate indeed.''

Japan rests atop one of the most complicated geographical structures in the world and is prone to quakes because it sits at the meeting point of several key tectonic plates, massive slabs that make up the earth's crust.

No One Can Predict

Geologists say two major plates -- the Philippine Sea plate and the Pacific plate -- are trying to force their way under the Eurasian and North American plates in the general area of Japan.

The plate movements are pulling Hawaiian islands toward Japan at a rate of about three inches (seven cm) a year, some recent studies have shown.

According to the widely accepted ``elastic rebound hypothesis,'' the Philippine Sea plate is pulling down the lip of the Eurasian -- like someone bending a plastic ruler by bending it over the edge of a table.

People in Japan know all too well that when the ``ruler'' bends too far it will spring back, causing a massive earthquake.

The whole nation is vulnerable, but the possibility of a quake flattening the nation's economic, political and population center of Tokyo causes the greatest anxiety.

But few see the activity in Izu as a precursor to such a disaster. Those quakes have been caused mainly by volcanic activity loosening bits of the plates under the island chain.

The plates are so large and their movements so complex that many geologists say there is no scientific basis for saying that the rather shallow Izu island events will lead to a cataclysmic disaster somewhere else along the plate.

Retired General Toshiyuki Shikata, who is advising Tokyo Governor Shintaro Ishihara on the metropolis' own disaster drill set for Sunday, said this week predicting quakes remained basically a guessing game.

``As for whether an earthquake in Tokyo is imminent, not even experts at the University of Tokyo can predict that,'' he told a media luncheon.



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