A Japanese rescuer walks across an area devastated by the tsunami in Sendai on March 13, 2011. Researchers are debating over whether the earthquake could have put Japan at a greater risk of a 'mega-quake'.
Credit: AFP
PARIS: Seismologists are comparing data 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.
Experts said it was too soon to know if the tectonic upheaval that shook northeast Japan and unleashed a 10-metre 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 seismologist with the Swiss Seismological Service in Zurich. But - one way or the other - it is almost sure to have an impact, experts agree.
Japan haunted by big earthquakes
The Japanese government's Earthquake Research Committee has long warned that Tokyo faces a serious risk of a major quake - 8.0 or higher - in the coming decades.
Japan 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.
"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.
Redistributing stress
An earthquake doesn't always relieve stress - sometimes it redistributes it, he said. "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 km northeast of Tokyo - would stress levels have relaxed, he said. "An increase in loading" - added pressure - "could advance the date of a future quake near Tokyo”, he added.
Follow up
There's a bleak warning. I hope you do a follow up article when the research is complete detailing whether Tokyo and the wider region are at greater (or diminished) risk of an earthquake in the immediate future.