Japanese Earthquake - was it really that devastating?

Astronuc

Someone on another site posted a figure from a site looking at an increase in earthquake activity in the long term.

http://www.earth.webecs.co.uk/

USGS also looks at trends. Here are some statistics.
http://earthquake.usgs.gov/earthquak...ear/graphs.php

It's noisy - but there seems to be a slight increase in frequency of strong earthquakes of 8 or greater since 1990. Any long term increase could also reflect an improvement in monitoring.

Some of the oldest nuclear plants were built in the 1960's/1970's, and thus reflect a seismic activity assessment up to that point.

I have to wonder if things have changed a little along the western Pacific Ring of Fire, or in generally around the ROF.

davenn

thats only really a short term view, if you look at long term trends 100 - 200 yrs the avg hasnt changed.
On avg there is still only 1 x M8+ / year and ~ 15 x M7.0 - 7.9 / yr

2004 was a bit of an anomaly in the big scheme with 4 events > than M8


Dave

lark

The Japanese earthquake wasn't just "rather strong", it was gigantic! Magnitude 9.
For comparison the "Big One" that's expected to strike Los Angeles soon would be about a magnitude 8. That's 1/32 as much energy as this earthquake! The San Andreas fault near Los Angeles is capable of about that size of an earthquake.
I've read that this may have been a once in a millenium event for Japan. A similarly gigantic tsunami struck Japan in 869.
Areas of Japan that were above sea level are now below ...
Maybe there will be new lakes.
Laura

Calrid

I think off the top of my head, the largest known magnitude was 9.5 in South America this was a puppy in comparison to that but then it's a pretty big puppy!

joelupchurch

Does anyone have experience in interpreting USGS shakemap data? I was trying to guess-estimate the g forces at the Fukushima Daiichi reactor during the quake and someone directed me to the usgs data. I seem to have to be having some problem understanding it.

http://earthquake.usgs.gov/earthquak...hake/c0001xgp/

When I click through to the underlying data, I seem to get something close to .6g for the Max Acc (%g) at the reactor.

http://earthquake.usgs.gov/earthquak...t.html#sFKS001

FKS001, which is closer to the epicenter reported Max Acc (%g) 63.1432 and FKS004, which is further away reported 57.9340. I used 37.421 141.032 as the location of the reactor. The distances to the epicenter in the table appears to be wrong. It is much smaller than what I get in Google Earth or what the USGS is reporting.

http://earthquake.usgs.gov/earthquak...11/usc0001xgp/

Is there a difference between Peak Acceleration and Max Acceleration? Nuclear reactors usually deal with Peak Acceleration. I'm also a little concerned about the "Not Reviewed by Human" caption on the shakemap.

davenn

yes interesting, the distances are VERY wrong. event the closest point on the coast, directly west of the epicentre is ~ 95km !!

Difference between Peak and Max I suspect you will find Peak = an instantaneous reading, whereas Max is an intergrated, over several seconds, reading
I have been known to be wrong haha ;) unfortunately I dont have any contact with my university geology professors any more. But I guess an email to the USGS would soon clear that up. As well as the distance problem.

Dave

joelupchurch

The only thing I could think of, is that the routine that they are calling is returning a result in miles or nautical miles and they are labeling it kilometers. Getting your units mixed up is a popular way to shoot yourself in the foot. It could be hard to catch if no one was using it in their calculation.

megumi norito

what's crazy is that japan was actually prepared for a tsunami and something like this......at least they thought!!....i wonder how prepared we are?...i also wonder if they are going to raise gas prices even more now , blaming this???

joelupchurch

The two reactor plants most at risk are San Onafre and Diablo Canyon. San Onafre has a 30 foot seawall and Diablo Canyon is at the top of a cliff, so it looks like they certainly considered it. These reactors are PWR and frankly make the BWR in Japan look flimsy. Diablo Canyon is more problematic since there are active faults in the area.

Here is a list of all the US Reactors with a Google map at the bottom.

http://world-nuclear.org/NuclearData....aspx?id=27569

nismaratwork

I'd just point out, a massive quake would do a lot, but nothing like a tsunami. It was, we have to remember, the tsunami that nailed Fukishima.

lark

Geologists actually didn't expect that fault to have such a big earthquake. http://sciencenews.org/view/generic/...ion_a_surprise People were not prepared at all for the giant tsunami that resulted. A similarly huge tsunami happened in 869 and in 2001 researchers predicted another one was about due. http://wwwsoc.nii.ac.jp/jsnds/contents/jnds/23_2_3.pdf

I don't think they could have built a seawall that would shut out such a powerful tsunami. All they could have done would be to not live at low elevations right next to the ocean, or have some kind of incredibly good and fast warning system.

As well as being a huge shock, the quake was optimized to produce a big tsunami, because it had a shallow focus, according to the Japan Meteorological Agency.

I wonder what they are going to do with the large ships that were carried inland by the tsunami. Leave them there are museums?

Laura

nismaratwork

I suspect they'll be treated as debris... they'll definitely make some kind of memorial, but I suspect it would be more understated than a large vessel.

lark

I mean, ships are built near the water. It would be rather hard to tow such a thing around.

joelupchurch

I suspect the ships will have to be cut up and hauled off as scrap. Some of the boats might be hauled back to sea if they are repairable.

lark

I think leaving a large ship there as a memorial, with a museum built into it and all sorts of pictures of the disaster and tsunami devastation, would be rather beautiful.

Like this one: http://i.telegraph.co.uk/multimedia/...0_1852083i.jpg

It needs to be fixed up a little, but I wouldn't waste the tsunami's efforts, rather route the road around it and turn it into a spectacular tourist attraction. Japan is going to need tourist attractions ...

davenn

That really shows his lack of understanding of megathrust systems and their potentials !

quote...“This area has a long history of earthquakes, but [the Sendai earthquake] doesn’t fit the pattern,” says Harold Tobin, a marine geophysicist at the University of Wisconsin–Madison. “The expectation was high for a 7.5, but that’s a hundred times smaller than a 9.0.”

that almost makes me laugh. Wonder what sort of marine geophysicist he is ? maybe he doesnt specialise in plate tectonics ?
Any, I repeat ANY major thrust system is capable of producing such events, That is just a given especially when you look back in history at the different regions around the Pacific and Indian Oceans.

Cheers
Dave

nismaratwork

It would have to be removed, cleaned, drained and scrubbed first, then replaced. Knowing the Japanese I'd suspect something made from a ship, not a whole ship itself. One is a reminder, the latter is a momument.