I have been reading here and there that both strength of earthquake and height of tsunami at Fukushima Daiichi were exaggerated and that the disaster is man-made. Here’s my summary up to now on this subject. (Links on this post will open in new windows.)

About Tsunami Height:

This is an article dated May 21, 2011 at Asahi.com I came across recently.

Analysts dispute TEPCO’s estimate of height of tsunami:

In the article, some experts agree TEPCO assessment 14-15 meter tsunami and others do not and estimate about 10 meter tsunami.

Difference between 14-15m and 10m is important.

In a letter to the government-appointed panel overseeing the Fukushima compensation issue on April 25, TEPCO said: “Given that the tsunami was so large that it reached a height of 14-15 meters, there is good room for an interpretation that it amounted to an ‘extremely large-scale act of God.’ ”

The utility is arguing that the law on compensation for nuclear accidents gives it immunity from compensation liability in such a case.

Now you know why it’s important.

Here’s another quote from the same article:

Yasuhiro Suzuki, professor of geomorphology at Nagoya University, analyzed satellite photos with his coworkers.

They only found traces of water reaching a height of about 10 meters on a gently sloping road several hundred meters from the reactor buildings.

“The sustained depth of water in the buildings was probably a maximum of around 10 meters,” Suzuki said.

He said images that appear to show that water had reached up to 15 meters in areas of the plant may be misleading. “These are probably waves that ran up locally after clashing against buildings,” he said.

Another important point from the article:

Meanwhile, the 2011 Tohoku Earthquake Tsunami Joint Survey Group, an association of scientists, said the height of the tsunami was less than 10 meters in the Fukushima Prefecture area.

The scale of a tsunami can be amplified in a particular location by coastal topography, but Imamura said, “There appears to be no particular reason for the tsunami to be amplified just there.”

To understand argument on tsunami heights, I found that there are a couple of definition of heights on tsunami we need to know:

  • Inundated height
  • Run-up height
  • Inundated depth

I found following document easy to understand what they are talking about. Scroll down for three points I listed.

Tsunami Impacting Eastern Japan and Preparedness for Extraordinary Natural Disaster 5/25/2011 by Port and Airport Research Institute in Japan

http://www.pari.go.jp/en/files/items/3733/File/2011052327IAPH.pdf (It may take long to open. Save and open from your local file is faster.)

  • GPS mounted wave-buoy
  • Tsunami height measured and estimated
  • Effect of break water

Fukushima Daiichi nuclear plant is located between Soma port and Onahama port in South (lower part of the maps)

Coast line around Fukushima prefecture is not like rugged coast line further north which might caused significant difference of tsunami height in particular spot.

According to their data, estimated tsunami heights (estimated inundated heights along the shoreline ) along Fukushima prefecture do not exceed 10m at any point.

Following is drawing by TEPCO:

Result of the Investigation on Tsunami at Fukushima Daiichi Nuclear Power Station:

In the TEPCO link, inundation height says approximately +14-15m. That means water passed 8.3 – 9.3m above the seawall, more than twice the height of the seawall above water (5.7m).

Next are links of photos of tsunami released by TEPCO. Do you see water is more than twice of the height of the seawall?

And this is a video an employee who was working at No. 4 took while running.

福島第一原発を襲う10mの津波映像!! Moment,tsunami attacks”Fukushima Nuke Plant”:


I doubt if the tsunami was even 10m high, even after watching the dramatic video with tsunami topping the seawall with high white spray.

A local citizen’s group requested TEPCO at a meeting that TEPCO correct tsunami height as they erroneously represented “run-up height” as “tsunami height” in their report to Japanese government. In turn, Japanese government reported to IAEA based on TEPCO report.

About Strength of 3.11 Earthquake:

Magnitude 9.0 –

Magnitude 9.0 was at the epic center 70 kilometres (43 mi) east of the Oshika Peninsula, further north from Fukushima Daiichi. Seismic Intensity around the area was 6+ according to Japan weather agency and that is what should count.

The 2011 off the Pacific Coast of Tohoku EarthQuake
Distribution of JMA Seismic Intensity


To give you an idea, Hamaoka nuclear plant south west of Tokyo had been considered most dangerous nuclear plant because there is high probability that magnitude 8.0 + earthquake hit with its epic center directly under or near under the plant in next 30 years.

In Japan earthquakes of seismic intensity 6+ are not that uncommon They would expect any decent building, let alone nuclear plant, takes that in design consideration.

At early stage I was reading posts by anonymous poster who said he was at No. 1 reactor when the earthquake hit that the plant had problems after the earthquake, even before tsunami hit and suspect the same at other reactors.

Here’s a good investigative report on the subject:

Meltdown: What Really Happened at Fukushima?

Implication that the reactors/containments did not fair well under seismic intensity 6+ is serious:

Either design flaw, aging material problem or even faulty construction.

  • Failed two reactors (No.1 and No. 2) were supplied by GE, No. 3 by Toshiba, No, 4 by Hitachi and all containment’s are GE MARK I.
  • All reactors started operating in 1970s.
  • It is common practice in Japan to build nuclear plants using many unskilled laborers including local farmers or fishermen hired by subcontractors, to help local economy for one reason.

But all potential problems which might led to the disasters will be forgotten, once it became official finding that everything worked fine as planned until the huge tsunami hit the plant caused by the unprecedented earthquake.

The narrative repeated by TEPCO “14-15m tsunami caused by 9.0 magnitude earthquake destroyed their plant” has been repeated by media, academia, nuclear industry without any examination seems to have become “fact”.

It is very convenient to everybody concerned. Isn’t it?

Links to some reports which premise is all based on the TEPCO narrative:

Japanese Government

Report of Japanese Government to the IAEA Ministerial Conference on Nuclear Safety – The Accident at TEPCO’s Fukushima Nuclear Power Stations –



Recommendations for Enhancing Nuclear Reactor Safety in the 21st Century
The Near-Term task Force Review of Insights from Fukushima Dai-Ichi Accident



Technical Lessons Learned from the Fukushima-Daichii Accident and Possible Corrective Actions for the Nuclear Industry: An Initial Evaluation


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