Posts Tagged ‘2011 Tōhoku earthquake and tsunami’

Great Tohoku quake in 2011 caused standing waves in Norwegian fjords 30 minutes later

August 13, 2013

Seismic seiches are standing waves set up on rivers, reservoirs, ponds, and lakes when seismic waves from an earthquake pass through the area. They are in direct contrast to tsunamis which are giant sea waves created by the sudden uplift of the sea floor.”

A new paper describes how these seiches -standing waves – observed in the Norwegian fjords in 2011 – for the first time since the 1950’s – have been linked to the Great Tohoku Quake of 2011 half an hour earlier.

Stein BondevikBjørn Gjevik and Mathilde B. Sørensen, Norwegian seiches from the giant 2011 Tohoku earthquake, Geophysical Research Letters, DOI: 10.1002/grl.50639, 2013

Abstract: Seismic waves of the giant 2011 Tohoku earthquake triggered seiches in western Norwegian fjords. The seiching began a half hour after the earthquake origin time. The oscillations were noted by eyewitnesses and recorded by surveillance and cell phone cameras. The observations show maximum trough-to-peak amplitudes of 1.0–1.5 m and periods of 67–100 s. The water waves were not triggered from the arrival of the surface waves, the timing inferred for other seiches. Instead, the seiching began during the passage of horizontal waves. We reproduced the S wave trigger by means of a shallow-water wave model calibrated previously to Norwegian tides and storm surges. The simulations, which used the observed earthquake motion as forcing, show water waves with periods and amplitudes similar to those in the film clips. However, the strongest horizontal ground oscillations with shorter periods (20–30 s) did not contribute much to the formation of the seiches.

It is not the first time that such standing waves have been observed so far away. As the US Geological Service notes:

The term seismic seiche was first coined by Anders Kvale in 1955 to describe oscillation of lake levels in Norway and England caused by the Assam earthquake of August, 1950. But this was not the first time that seismic seiches had been observed. The first published mention was after the great earthquake of November 1755 at Lisbon, Portugal. An article in Scot’s Magazine in 1755 described seiches in Scotland in Loch Lomond, Loch Long, Loch Katrine and Loch Ness. They were also seen in English harbors and ponds and were originally described in the Proceedings of the Royal Society in 1755.

…….

Seismic waves from the Alaska earthquake of 28 March, 1964, were so powerful that they caused water bodies to oscillate at many places in North America. Seiches were recorded at hundreds of surface-water gaging stations – although they had rarely been reported following previous earthquakes. Indeed, four seiches were observed in Australia.

Some of the 1964 seiches were very large. Waves as high as 1.8 meters were reported on the Gulf Coast – probably because they were generated in resonance with the seismic surface waves.

In the case of the Norwegian fjords and the Great Tohoku quake, PhysOrg reports:

The scene was captured by security cameras and by people with cell phones, reported to local media, and investigated by a local newspaper. Drawing on this footage, and using a computational model and observations from a nearby seismic station, Bondevik et al. identify the cause of the waves—the powerful magnitude 9.0 Tohoku earthquake that hit off the coast of Japan half an hour earlier.

In closed or semi-enclosed bodies of water, seismic waves can trigger standing waves known as “seiches.” Seiching had not been recorded in Norway’s fjords since 1950. Scientists have traditionally thought that seiching is caused by seismic surface waves, but the authors find that the fjord seiching was initiated before the surface waves had arrived.

Using seismic observations and a model for local fjord behavior, they find that in this case the seiching was triggered by S waves, which travel through Earth’s body, and later was amplified by Love waves, which travel on Earth’s surface. There are a lot of open questions surrounding the connection between earthquakes and seiching, but the authors’ research supports the idea that not all earthquakes will cause seiching in all enclosed bodies of water. The occurrence of the Japanese earthquake?induced seiches depended on the period and orientation of the seismic waves aligning with the natural frequency and orientation of the body of water.

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Two years on and Japan returns to nuclear power

March 11, 2013

It is two years today since the Great 2011 Tohoku Earthquake and Tsunami and the meltdown at 3 reactors of the Fukushima Daiichi nuclear plant.

It was the most powerful known earthquake ever to have hit Japan, and one of the five most powerful earthquakes in the world since modern record-keeping began in 1900. The earthquake triggered powerful tsunami waves that reached heights of up to 40.5 metres in Miyako in Tōhoku’s Iwate Prefecture and which, in the Sendai area, travelled up to 10 km inland. The earthquake moved Honshu (the main island of Japan) 2.4 m  east and shifted the Earth on its axis by estimates of between 10 cm  and 25 cm.

On 12 September 2012, a Japanese National Police Agency report confirmed 15,881 deaths, 6,142 injured and 2,668 people missing across twenty prefectures, as well as 129,225 buildings totally collapsed, with a further 254,204 buildings ‘half collapsed’, and another 691,766 buildings partially damaged. … 

The tsunami caused nuclear accidents, primarily the level 7 meltdowns at three reactors in the Fukushima Daiichi Nuclear Power Plant complex, and the associated evacuation zones affecting hundreds of thousands of residents.

In the knee-jerk reaction to the Fukushima accident all Japan’s 50 nuclear reactors in operation were shut down. Ongoing nuclear power plant projects were suspended. The global debate was more an emotional wave rather than rational discussion. The fear was real of course but what was generally ignored was that while the earthquake and tsunami killed some 18,000 the Fukushima accident did not cause any direct radiation related fatalities. The reality is that the Fukushima reactors were designed in the 1960’s and yet managed to survive the magnitude 9.1 earthquake but they could not cope with and succumbed to the massive tsunami. After the earthquake the reactors were actually shut down – automatically and in good order – but the emergency power to the cooling systems were knocked out by the subsequent tsunami. The failure was a failure of anticipating and designing for a tsunami that was as large and as powerful as it was. Tsunami’s as large as the 2011 event have occurred in Japan roughly every 1000 years. The Fukushima failure was not so much a fault of the nuclear plant as the failure of the designers in anticipating a sufficiently large tsunami within the lifetime of the plant.

But two years on, some rationality is returning to the debate. Two reactors have been turned back on and construction has gingerly been restarted on the new 1383 MW advanced boiling-water reactor at Oma.

Map credit Washington Post

Washington Post: 

In the aftermath of March 2011 meltdowns in Fukushima that contaminated 700 square miles with radiation and forced 150,000 to flee their homes, most never to return, Japan’s utility companies paused nearly all nuclear-related projects. The accident sparked a global debate about nuclear power, but it was especially fierce in Japan, where all 50 operable reactors were taken offline and work was halted on three new plants where building had been underway.

But two of the existing reactors are back in action, and the resumption of construction at the Oma Nuclear Power Plant here — a project that broke ground in 2008 and was halted by the operator, J-Power, after the accident — marks the clearest sign yet that the stalemate is breaking. ….. 

At the national level, Japan has cycled through three prime ministers since Fukushima — the first fiercely anti-nuclear, the next moderately anti-nuclear, the current one cautiously pro-nuclear. The previous ruling party tried last fall to plot a nuclear phaseout by the 2030s, but anti-nuclear advocates say the pledge was watered down to the point of being meaningless. The new prime minister, Shinzo Abe, plans this month to convene the latest in a series of expert panels to help overwrite the phaseout plan, and its makeup suggests that he prefers a role for nuclear power.

Japan’s anti-nuclear movement, which swelled after the Fukushima accident, could still play a role, but it is politically disorganized and has grown quieter in recent months. Individual activists cite the resumption at Oma as controversial but note that the move did not prompt mass-scale protests. ….. 

 

One year on from the Great Tohoku earthquake and tsunami

March 11, 2012

One year on and young hopes bloom eternal.

Illustration by Yuko Shimizu

Young hopes bloom eternal: Illustration by Yuko Shimizu: From The Japan Times

I was in Japan during the Great Hanshin Earthquake in 1995 when over 6,000 perished in Kobe and – inevitably – I try to relate events to my own experience. But the Graeat Tohuku earthquake and tsunami were something quite different and have claimed more than 20,000 lives.

The death toll was much greater after the Aceh earthquake and tsunami but was spread over many more countries and in that sense is more “diffuse”. Perceptions sometimes get diluted compared to the intensity of the reactions one year ago. The 2004 Indian Ocean earthquake and tsunami claimed over 230,000 lives in 14 countries.

The meltdowns at the Fukushima nuclear plant following the Tohoku earthquake and tsunami were pretty scary but sometimes the coverage (especially in Europe) becomes alarmist and tends to take away from the earthquake and tsunami. But it is worth remembering also that the incidents at Fukushima  – without trying to trivialise them – have caused no radiation related deaths.


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