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Tsunami Caught Japan's Nuclear Industry Off Guard - NYTimes.com
After an advisory group issued nonbinding recommendations in 2002, Tokyo Electric Power Company, the plant owner and Japan's biggest utility, raised its maximum projected tsunami at Fukushima Daiichi to between 17.7 and 18.7 feet -- considerably higher than the 13-foot-high bluff. Yet the company appeared to respond only by raising the level of an electric pump near the coast by 8 inches, presumably to protect it from high water, regulators said.

Hm!? The Areva presentation quoted upthread speaks of 7 m high retaining walls designed to protect against 6.5 m tsunamis. That's no contradiction with the 5.7 m maximum expected tsunami above, but it is with the 4 m high bluffs, unless someone confused those with the retaining walls, or the Areva guy got erroneous information.

Regarding the article's main point, that earthquake and tsunami risk assessment was based on the largest even in the historical record rather than probability assessment, I note that the same is true for many European plants.

*Lunatic*, n.
One whose delusions are out of fashion.

by DoDo on Wed Mar 30th, 2011 at 04:56:10 AM EST
[ Parent ]
DoDo:
risk assessment was based on the largest even in the historical record rather than probability assessment
That's a robust statistical method. No "probabilistic assessment" will provide a reliably better estimate than the "largest historical event" (which is also a statistical assessment).

So, in what may be my last act of "advising", I'll advise you to cut the jargon. -- My old PhD advisor, to me, 26/2/11
by Carrie (migeru at eurotrib dot com) on Wed Mar 30th, 2011 at 05:17:32 AM EST
[ Parent ]
When the largest possible quake at a rupture zone happens every few thousand years and the historical record reaches back a few centuries, I don't think the historical record suffices. (Which doesn't mean that one shouldn't call paleoseismology for help; the NYT article does mention new data about a tsunami in the 9th century that wasn't used for re-assessments.)

*Lunatic*, n.
One whose delusions are out of fashion.
by DoDo on Wed Mar 30th, 2011 at 05:34:01 AM EST
[ Parent ]
Does "the historical record" for Vesuvius include the Pompey eruption, or just the last 200 years?

So, in what may be my last act of "advising", I'll advise you to cut the jargon. -- My old PhD advisor, to me, 26/2/11
by Carrie (migeru at eurotrib dot com) on Wed Mar 30th, 2011 at 05:43:03 AM EST
[ Parent ]
If you ask about the related earthquake, I don't know, if the volcano eruption, yes but what's the relevance.

*Lunatic*, n.
One whose delusions are out of fashion.
by DoDo on Wed Mar 30th, 2011 at 06:28:58 AM EST
[ Parent ]
That "historical data" includes presumably all known events at the time the study is made.

For Earthquakes there's the Gutenberg-Rischter probabililistic model, but for Tsunamis all there is is the historical, archaeological or paleogeological record.

So, in what may be my last act of "advising", I'll advise you to cut the jargon. -- My old PhD advisor, to me, 26/2/11

by Carrie (migeru at eurotrib dot com) on Wed Mar 30th, 2011 at 06:46:36 AM EST
[ Parent ]
ARGeezer:
According to the researcher, Yukinobu Okamura, and the records of a government council where he made the warning, TEPCO asserted that there was flexibility in the quake resistance design of its plants and expressed reluctance to raise the assumption of possible quake damage citing a lack of sufficient information.

...

Okamura had warned in 2009 of massive tsunami based on his study since around 2004 of the traces of a major tsunami believed to have swept away about a thousand people in the year 869 after a magnitude 8.3 quake off northeastern Japan.

He had found in his research that tsunami from the ancient quake had hit a wide range of the coastal regions of northeastern Japan, at least as far north as Ishinomaki in Miyagi Prefecture and as far south as the town of Namie in Fukushima Prefecture -- close to the Fukushima Daiichi plant -- penetrating as much as 3 to 4 kilometers inland.



So, in what may be my last act of "advising", I'll advise you to cut the jargon. -- My old PhD advisor, to me, 26/2/11
by Carrie (migeru at eurotrib dot com) on Wed Mar 30th, 2011 at 06:55:02 AM EST
[ Parent ]

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