Tokyo 'has 70% chance of powerful earthquake within four years'

[xchrom]

http://www.guardian.co.uk/world/2012/jan/23/tokyo-powerful-earthquake-four-years

Experts in Japan have warned that the chances of a powerful earthquake striking Tokyo in the next four years could be as high as 70%, a more alarming scenario for the city's 13 million people than predicted by the government.

The earthquake research institute at Tokyo University said that in the worst case, a quake of magnitude 7 would hit the southern part of metropolitan Tokyo by 2016, while the chances of a similar disaster occurring within 30 years are as high as 98%.

The government, by contrast, estimates the possibility of an earthquake that size striking the capital at 70% in the next three decades.

The warning comes less than a year after a magnitude-9 earthquake off the country's north-east coast triggered a tsunami that left about 23,000 people dead or missing.

[Yo_Mama]

1. But that's not what the study says

The headline doesn't fit with the study. The study used extrapolations in a computer model. Using the most negative (risky) inputs yields the 70% chance. That should be a high bound.

I think they are unquestionably correct in saying that the stresses have increased as a result of the 3/11 quake, and that the Tokyo area is at higher risk than it was before. Quantifying that is very difficult - if the higher current rate of relatively small quakes relieves stresses, it may not happen.

Jumping to another, but unfortunately related, issue - the Hamaoka NPS is not going to be restarted, no matter what the government says. The risks have only increased, and even if the entire plant came through a big quake with no significant damage, it would still have to be shut down for an extended period precisely when they needed power the most. If a quake in the southern Tokyo region occurs, it is going to raise the risks on the Hamaoka fault too. It's just a huge liability. Chubu is going to have to write it off.