By Dan Satherley and Talia Blewitt, with AP
It has been one year since the 9.0 magnitude Tōhoku earthquake that triggered a devastating wall of water off the northeastern coast of Japan's largest island, Honshu.
View photos one year on from the quake
Almost 16,000 people were killed in the resulting tsunami, including 19 foreigners, and over 6,000 injured. More than 3,000 people are still listed as missing.
The earthquake struck just before 3pm on March 11, a Friday afternoon. The quake was centred 70km east of the Oshika Peninsula (about 373km northeast of capital Tokyo), and was 32km deep.
A surge of water ranging from six to 40 metres high hit the prefectures of Iwate, Miyagi and Fukushima, while further north the prefecture of Hokkaido suffered swells of nearly three metres.
In addition to the human casualties over 125,000 buildings were damaged or destroyed. The World Bank estimated the economic cost to be US$235 billion, the most expensive natural disaster on record.
THE QUAKE
The Tōhoku quake was one of five largest earthquakes since recording began in 1900, measuring magnitude 9.0.
Seismologists now know it was a ‘reverse fault’, where the upper part of a faultline is thrust over the foot of the other. The fault leaped across gaps and other boundaries along the fissure, creating a massive amount of force.
The North American plate slid over the Pacific Plate along a subduction zone (the sideways and downward movement of the plate’s edge) running 130km off the Pacific coast of Japan. It occurred near the Japan Trench, although it was beneath the offshore shelf and not the trench itself.
The shock was so great that the fault zone extended 400km and increased the intensity of energy 30-fold.
As this occurred only 32km down, the seabed shot violently upwards, producing the surge which created the tsunami.
Tsunami waves came ashore as far away as South America, damaging 200 homes in Chile, and the US, where one man was swept out to sea.
Waves also hit Antarctica, strong enough to break an iceberg the size of Manhattan off the Sulzberger Ice Shelf.
While some Japanese seismologists were as shocked as anyone else when the earthquake occurred, others said it was inevitable.
Placed on the Pacific Ring of Fire, Japan’s geophysical network is closely monitored, and it's believed thousands of lives were saved by the country's Earthquake Early Warning system.
Japan is precariously situated on a series of tectonic faultlines – the north end of the country is on the North American Plate, the southern end on the Eurasian Plate, and the edge of the Pacific and Philippine Sea Plates are also close.
There are also other minor plates in the region – the Amur, Yangtze and Okinawa.
Geographically it is similar to New Zealand, if not more threatened by the variety of fault lines in the region.
FUKUSHIMA
Reactors at nuclear power plants across Japan's east coast automatically shut down, including those at Fukushima, and emergency generators were used to cool them down.
Unfortunately, they were only rated to withstand tsunami waves up to 5.7m, and when a 14m-high wave struck, the generators ceased working and the three reactors functioning at the time of the quake began to overheat.
Three of the reactors at the plant experienced full meltdown, and a series of hydrogen explosions ensued.
A 20km evacuation zone around the plant was ordered, affecting 100,000 people. The level of radiation released into the atmosphere has been measured at about one-tenth that of the Chernobyl disaster, but it is estimated between 100 and 1000 people will die in the future from cancer as a result of radiation exposure.
The decontamination at Fukushima is expected to take around 40 years.
DAMAGE
The sheer amount of damage to the country's infrastructure was hard to fathom. In April 2011, it was estimated over 45,000 buildings had been completely destroyed and nearly 150,000 damaged, including 300 hospitals. Nearly 4.5 million houses were left without power, as a quarter of the country's electricity generation had been knocked offline.
Parts of eastern Japan will be without electricity for many years, as the country's power grid is split down the middle into two largely non-compatible networks.
Damage in Tokyo, where many seismologists expected 'the big one' to strike, was minimal. Striking 373km away, by the time the waves hit the capital, it measured just under magnitude 6 – representing an at least 1000-fold drop in intensity.
The city did experience liquefaction however, and around 30 buildings were destroyed and 1000 damaged.
The city of Sendai, one of the closest to the quake's epicentre, lost hundreds in the quake, but its centre went relatively unscathed.
Ishinomaki, a city on the coast of the Miyagi prefecture, was heavily hit. Over 3,000 lost their lives, including almost the entire student body and staff of a primary school, and nearly the same number are still missing. Almost half the entire town ended up underwater.
The entire city also dropped by 1.2m, causing flooding during high tides.
ONE YEAR ON
Some areas hit hard by the tsunami have showed remarkable recovery. Streets covered in debris, upturned cars and stranded boats have been transformed back into what they were before the quake, with little evidence anything ever happened.
But although much of the visible damage has been cleared, the impacts on residents' health and the economy linger.
People living on the outskirts of the 20km evacuation zone around the Fukushima plant go out of their way to buy food and water from non-local sources, and no one really knows what the long-term effects of low, but constant, radiation exposure will be.
Around 280,000 people still live in Fukushima.
The fishing industries in Miyagi, Iwate and Fukushima were almost completely destroyed and big Japanese companies like Nissan, Sony, Toyota and Honda had to temporarily halt production.
The country's economy contracted 3.7 percent in the quarter, and has struggled to bounce back. In the last few months of 2011 the economy contracted 0.7 percent, exceeding expectations and providing hope the turnaround is coming.
Economists forecast 1.5 percent growth this quarter.
DEBRIS WASHED OUT TO SEA
Refrigerators, TVs and other debris dragged into the sea could show up in remote atolls north of Hawaii by the end of this year, with other pieces reaching parts of the west coast of the US in 2013 and 2014.
Debris from the tsunami initially formed a thick mass in the ocean of Japan's northeastern coast. But ocean currents have dispersed the pieces so they're now estimated to spread out some 4,5000km halfway across the Pacific.
The National Oceanic and Atmospheric Administration says the first pieces of tsunami debris are estimated to make landfall on small atolls northwest of the main Hawaiian Islands. Other pieces are expected to reach the coasts of Oregon, Washington state, Alaska and Canada between March 2013 and March 2014.
Last September, a Russian training ship spotted a refrigerator, a television set and other appliances west of Hawaii. By now, the debris has likely drifted so far apart that only one object can be seen at a time, said Nikolai Maximenko, a University of Hawaii researcher and ocean currents expert.
Most items likely sank not far from Japan's eastern coast.
One million to 2 million tonnes of debris remain in the ocean, but only 1 to 5 percent of that could reach American and Canadian shorelines, Maximenko said. The tsunamis that followed the earthquake generated between 20 million and 25 million tonnes of debris, including what was left on land.
There is little chance of any debris being contaminated by radiation. The debris came from a large swath of Japan's northeastern coast, not only near the tsunami-damaged nuclear power plant in Fukushima. Further, it was dragged out to sea with the tsunamis, not while the Fukushima plant experienced multiple meltdowns.
Nicholas Mallos, a conservation biologist and marine debris specialist for the Ocean Conservancy, said many of the objects in the debris were expected to be from Japan's fishing industry. That could pose a risk for wildlife, such as endangered Hawaiian monk seals, if fishing gear washes up on coral reefs or beaches.
"The major question is how much of that material has sank since last year, and how much of that remains afloat or still in the water column," Mallos said.
Maximenko said the dispersion of the debris makes it more difficult to track but no less hazardous.
"In many cases it's not density that matters, it's total amount," he said. "For example, if there's a current flowing around Midway island, that island would collect debris like a trawl moving across the ocean. It will collect all the debris on its way."
Ultimately, Maximenko said, most of the remaining tsunami debris will join garbage floating in a gyre between Hawaii and California produced by swirling Pacific currents. Much of that trash in a wide area known as the Great Pacific Garbage Patch is bits of plastic, which slowly breaks down into smaller pieces but doesn't completely disappear. It was unclear whether large items like refrigerators will make it across the ocean because there has been little precedent for such an event.
COMPARISON TO CHRISTCHURCH
How does the scale of the disaster in Japan compare to that in Christchurch?
In terms of numbers, there isn't really much of a comparison. The quake in Japan measured magnitude 9.0, releasing 700 times more energy than the September 4, 2010 quake, and over 11,000 times more energy than the February 22, 2011 quake.
As mentioned above, at least 16,000 people lost their lives in Japan, compared to 185 in Canterbury (though the vast majority of those died in the tsunami rather than the quake itself).
The economic damage done to Japan has been estimated in the region of NZ$285 billion, with some estimates going as high as NZ$365 billion. The total cost of the Canterbury quakes has been estimated at between NZ$20 billion and NZ$30 billion.
Relative to the economy however, the impact on New Zealand was far greater. Treasury estimates the quakes to have cost around 10 percent of GDP, whilst the Japan quake only did "around 3 to 4 percent" of damage.
Canterbury has had more ongoing quakes – since September 4, 2010, there have been over 10,200 recorded shakes in the Canterbury region, with 45 of them measuring at least 5.0.
Since the March 11, 2011 quake in Japan, there have been far fewer shakes – just over 1800 – but around 650 of them have measured at least 5.0.
FUTURE EARTHQUAKE AND TSUNAMI CONCERNS FOR JAPAN
A similar situation to that of the Tōhoku quake is possible in the future when the Philippine Plate dives under the Eurasian Plate. This could create a series of shudders, coming from 100km or more southwest, for Tokyo. At this stage evidence of a tsunami like last year’s occurring is scarce.
The Economist highlighted Japanese media concern over other earthquakes which occurred in the days following the Tōhoku tremor. A quake of magnitude 6.6 between Nagano and Niigata prefectures, and a 6.1 in Shizuoka prefecture, sparked fear that the quakes were creeping closer.
Polls taken mid-last year show four in five Japanese are now "anti-nuclear", when as recently as 2005, 82 percent of Japanese backed nuclear energy. As of January 2012, 49 of the country's 54 reactors remained offline.
Former Prime Minister Naoto Kan earlier this year said he fears for Japan's existence if it continues to rely on nuclear energy.
Japanese researchers have also given a 98 percent likelihood a quake of magnitude 7 or greater will strike the Tokyo region in the next 30 years.
Japan is the world's top importer of energy supplies, as it lacks significant resources of its own, except for coal. It had reduced its reliance on imports by adopting nuclear energy, and a reversal threatens the country's economic recovery.
VIDEO
Footage of the quake as it happened
Japan's Parliament in session as the quake hits
Cars, bridges swept away by tsunami
Kiwi in Japan: 'Biggest I've ever felt'
Aucklander riding subway as quake hit
First reports of Fukushima nuclear emergency
Ship caught in tsunami-generated whirlpool
Explosions at Fukushima nuclear plant
Quake, tsunami death toll passes 10,000
Man saved from rooftop floating at sea
Japan - Before and after the tsunami
60 Minutes: Apocalypse Now
3 News / AP
source: newshub archive
