Quake could alter Tokyo risk: experts

March 11, 2011 by Marlowe Hood
People wait for transport services to resume at the Tokyo station as commuter trains stopped their services in the Tokyo metropolitan area. Seismologists were crunching data Friday to figure out if the magnitude 8.9 quake that rocked Japan increased the chances of a mega-quake hitting the Tokyo basin, home to 30 million people.

Seismologists were crunching data Friday to figure out if the magnitude 8.9 quake that rocked Japan increased the chances of a mega-quake hitting the Tokyo basin, home to 30 million people.

The Japanese government's Research Committee has long warned that Tokyo faces a serious risk of a major -- 8.0 or higher -- in the coming decades.

is still haunted by the "Big One" that devastated its capital in 1923 and left more than 140,000 dead. The 1995 Kobe quake, which claimed 6,400 lives, added to this ever-present fear.

Experts said it was too soon to know if the tectonic upheaval that shook northeast Japan Friday and unleashed a 10-metre (33-foot) tsunami put Tokyo at greater risk.

It could even reduce the odds of a killer quake hitting the capital.

"That is going to be hotly debated in the scientific community," said Jochen Woessner, a with the Swiss Seismological Service in Zurich.

But -- one way or the other -- it is almost sure to have an impact, experts agree.

"There will very likely be a strong interaction with the Kanto Plains," said John McCloskey, a professor of Geophysics at the University of Ulster in Northern Ireland, referring to the seaside basin that holds greater Tokyo.

An earthquake doesn't always relieve stress -- sometimes it redistributes it, he said by phone.

"Places that have not failed during a quake can actually be more stressed by the earthquake happening beside them. But we can't tell at this stage whether it has made the next earthquake more or less likely."

For Jerome Vergne, a seismologist at Strasbourg University in eastern France, "the risk for Tokyo cannot have diminished."

Only in the region north of the quake's epicentre -- some 400 kilometres (250 miles) northeast of Tokyo -- would stress levels have relaxed, he said in an interview.

"An increase in loading" -- added pressure -- "could advance the date of a future quake near Tokyo," he said.

A lone car rests among the remain of water on a street in Chiba city, suburban Tokyo. Seismologists were crunching data Friday to figure out if the magnitude 8.9 quake that rocked Japan increased the chances of a mega-quake hitting the Tokyo basin, home to 30 million people.

The Japanese capital is only 300 kilometres (200 miles) from an underwater "triple junction" where three of the two dozen tectonic plates that comprise Earth's constantly shifting crust meet.

Tokyo sits atop the Eurasian plate. Beneath it, the Philippine Sea plate descends, or subducts, from the south, while the Pacific plate slips down from the east.

Subduction is not a slow-and-steady process, but occurs in a "stick-slip" motion that gives rise to infrequent, but massive, convulsions.

A major earthquake in or near Tokyo could cause a trillion dollars in damage, experts have calculated.

Over the last decade scientists have developed computer programmes to measure stresses in Earth's outer layer in three dimensions, making it possible to see how those stresses might impact neighbouring faults.

People stand outside a building following a huge 8.8 magnitude quake to hit Japan in Tokyo. Seismologists were crunching data Friday to figure out if the magnitude 8.9 quake that rocked Japan increased the chances of a mega-quake hitting the Tokyo basin, home to 30 million people.

But it will be several days, perhaps weeks, before we know whether the tectonic time bomb sitting under Tokyo may have been reset, said Bob Holdsworth, a professor of structural geology at Durham University in Britain.

"When you have a big event on one fault, it affects the behaviour of adjacent faults," he said by phone. "The faults are, as it were, able to communicate with one another."

McCloskey said that the massive 8.9 quake Friday was, strictly speaking, an aftershock of a nearby 7.2 magnitude quake two days earlier, despite it far greater power.

"We have calculated that the stress field from the 7.2 quake on Wednesday is consistent with the triggering of this earthquake," he said.

But connecting the dots with the Tokyo region, several hundred kilometres distant, is far more difficult, he added.

Experts also look for patterns in the thousands of quakes that occur across the globe each year.

"Earthquakes are known to cluster, both is space and in time," Holdsworth said, pointing to recent quakes over 8.0 in or near Peru, Indonesia, China and Chile.

"There was a similar cluster spanning the period 1957-64, which included -- around the Ring of Fire -- the three biggest earthquakes on record," he said.

The Ring of Fire reaches from Indonesia to the coast of Chile in a 40,000 kilometre (25,000-mile) arc of nearly daily seismic violence around the Pacific rim.

Explore further: Mountain spine is a quake hotspot

Related Stories

Mountain spine is a quake hotspot

April 6, 2009

Scientists said a killer earthquake that struck central Italy on Monday occurred in a notorious trouble spot and warned further powerful shocks in the coming months could not be ruled out.

New Sumatra quake takes seismologists by surprise

October 1, 2009

The huge earthquake that hit Sumatra occurred at a deep, unexpected location, illustrating the dangerously complex geological mosaic in this area, a seismologist told AFP on Thursday.

Chile quake in 'elite class' like 2004 Asian quake

February 28, 2010

(AP) -- The huge earthquake that struck off the coast of Chile belongs to an "elite class" of mega earthquakes, experts said, and is similar to the 2004 Indian Ocean temblor that triggered deadly tsunami waves.

Rising risk of major quake in Chile: study

January 30, 2011

Central Chile faces increased risk of a very large earthquake close to the site of last February's 8.8-magnitude temblor that killed 520 people and cost 30 billion dollars, scientists said on Sunday.

Quake is 5th biggest, but Japan best prepared

March 11, 2011

(AP) -- Take the world's most earthquake-prepared country, jolt it with one of the biggest quakes in history and add a devastating tsunami minutes later. In the classic battle of Man vs. Nature, Nature won again.

Recommended for you

Global index proposed to avoid delays on climate policies

August 4, 2015

Professor David Frame, Director of Victoria's Climate Change Research Institute (CCRI), has co-authored a paper published today in the high profile international scientific journal Nature Climate Change. The paper argues ...

Study calculates the speed of ice formation

August 3, 2015

Researchers at Princeton University have for the first time directly calculated the rate at which water crystallizes into ice in a realistic computer model of water molecules. The simulations, which were carried out on supercomputers, ...

Researchers investigate increased ocean acidification

August 3, 2015

The primary cause of global ocean acidification is the oceanic absorption of CO2 from the atmosphere. Although this absorption helps to mitigate some of the effects of anthropogenic climate change, it has resulted in a reduction ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.