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Monday, 2 April 2012

Earthquakes

Hi,
I've had a draft of this written for a few weeks but didn't want to indulge in scaremongering. But after the big tremour last night - just as I was writing this blog - and in the light of yet another report and lots of media coverage, I decided to go ahead.

The aftershocks following the disaster last year tailed off after September but they increased in frequency after that one on New Year's Day - to the extent that I started carrying my transistor radio around with me again (when there's no electricity and no phones this is the only way to find out what's going on) .

The 3.11 disaster was caused out at sea when the edge of the North American plate (on which Japan stands) flipped up unleashing pressure built up against the Pacific plate which used to grind away under it in the same westerley direction. But now the geology has changed and the North American plate is moving east against the Pacific plate moving in the opposite direction. In the face of such realignment it's no wonder there are so many aftershocks, and over such a wide area. Apparently there have been 740 aftershocks over Force 5 in the last year, 4 times the number the year before.

A professor Hirata from The Earthquake Research Insititute of Tokyo University caused a stir a few weeks ago when he announced that there was a 70% chance of a Force 7 earthquake hitting Tokyo within the next 4 years. But it turns out that this was based on the frequency of aftershocks from March to September last year continuing at the same rate. Thankfully they're not so frequent and the official (Meterological Office) figure is 70% within the next 30 years.  But Force 7 is big. In a Force 6, the previous estimate, you crouch down and hang onto the furniture (that was what it was here). In a Force 7, the furniture starts jumping around.

Incidentally, the earthquake predicted for Tokyo has a different cause. The word you hear is  直下地震 (chokka jisshin), a 'direct earthquake' which sounds alarming but apparently it's an earthquake that occurs directly above its epicentre, along a fault.

The Great East Japan Earthquake was M9.1, magnitude being a measure of the amount of energy released. In Japan we also talk about 'force' (震度 shindo) which measures how it felt at a certain place. There are 600 monitoring posts throughout the country. So when there's an earthquake everyone switches on the TV or radio and NHK will announce the magnitude and whether there's risk of a tsunami, and then start to list how big it was at certain locations. It can get a bit boring after a bit as they reel off the names of towns and villages. If it's a big one, NHK will interrupt programmes but more often it's shown as surtitles on the screen. The other channels will interrupt programmes if it's really big otherwise they don't bother. NHK kindly waived licence fees for six months as our apartment was registered badly damaged. I felt bad as it was one of the few times I didn't begrudge paying the fee.

And then last Saturday, a new government report. This time regarding the Nankai Trough which goes from Shizuoka down to Kyushu. Worst scenario is for a M9 earthquake along the length of the trough. The whole area could suffer a Force 6 or Force 7, with tsunami over 20 metres. Worse, the tsunami could reach land in less than 10 minutes. As you can imagine, this has caused consternation. For example, at the time of the last survery in 2003, one town (Numazu) was predicted to have a tsunami of 6 metres so they built a sort of tower 12 metres high. Now they're told a tsumami could be 34 metres!

And of course, the first words on everyone's lips after a tremour are Genpatsu daijobu? (原発大丈夫? Are the nuclear plants alright?)This report is bound to fuel the controversy about whether to reopen the nation's nuclear plants. One example. The Hamaoka plant in Shizuoka has been closed but has 9,000 fuel rods. A new breakwater is being built, 18 metres high, but the new worst scenario is for a tsunami of  21 metres. Back to the drawing board.

'Preventing disaster' (防災 bosai) seems have given way to a new word 'damage limitation' (減災 gensai) . In the past people arrogantly thought their breakwaters would keep back the tsunami but these were washed away. Now people are thinking more practically with saving lives the priority. These long suffering people have a lot of work to do now rethinking how to live in this seismically active country.
Goodnight from a - touch wood - calm and steady Koriyama.
All the best
Anne



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