Japanese Earthquake and Tsunami 2011

Japan (Tohoku) 2011 Earthquake and Tsunami

Plates Involved and Boundary Type(s):

The Japanese Earthquake and subsequent Tsunami was caused by a release of energy at the ocean – ocean convergence between the Pacific and Eurasian Plates. The Pacific Plate is subducting under the Eurasian Plate off the east coast of Japan. This fault line is part of a larger area of fault lines called the “Ring of Fire”. The “Ring of Fire” is the cause of 90% of all Earthquakes and 75% of active volcanoes. This is due to the large amount of subduction that occurs in the area . The Japan trench approx. 130km from the coast of Sendai is part of this ring of fire. On March 11 2011 at 2:46pm a shallow violent earthquake about 24km into the crust occurred along the trench, due to the shallow nature of the earthquake most of the energy was released at sea level.

The earthquake occurred due to two reasons. The eastern side of the Pacific Plate contains a divergent boundary with the Nazca and Antarctica Plates. At this boundary convection current along with the Ridge Push are propelling the Pacific Plate in a north west fashion towards other plates including the Eurasian Plate which forms the subduction zone off the east coast of Japan. The subduction zone that is created by the Eurasian and Pacific Plate is the second reason or cause of the Earthquake. The Pacific Plate is subducting under the Eurasian plate because it is denser as asthenosphere has solidified to the bottom of it. Though over time, energy has built up from the process of subduction as the Pacific Plate continually caught on the Eurasian as it subducted and in March 2011 this energy was released. The Eurasian Plate that was caught on the Pacific Plate and being dragged down forming a trench through its subduction released in a thrust fault and moved approximately 50 metres horizontally and 10 metres vertically in the release. The earthquake sent ruptures along an area of subduction associated with the Japan Trench up to 300km long and 150km deep (This subduction zone is associated with the Eurasian and Pacific Plate). Scientists released reports later stating that the ruptures (slip) produced by the earthquake completely relieved the stress along the boundary.

The rupture and faulting of the Eurasian Plate caused it to move an unprecedented 50 metres horizontally. Scientists measured that the 9.1 magnitude Indian Ocean Earthquake of 2004 measured a slip of up to 25 metres even though it was a slightly bigger earthquake. The reason for this movement was the high levels of clay at the Japan Trench subduction zone. The clay that lines the sea floor in this area provided little resistance to the moving plates and hence the Eurasian plate didn’t stop for a massive 50 metres.

As a result of the release of energy from the subducting Pacific Plate under the Eurasian Plate, in March 2011, a magnitude 9.0 earthquake occurred that rocked Japan.  

Japanese Earthquake and Tsunami - Tectonic Impacts By Kyle Sier: https://www.youtube.com/watch?v=ibFEySTZi1g

Tsunami that followed:

In addition to the 50 metres of horizontal movement a 10 metre vertical movement coincided at the time of the Earthquake. This mass movement of the tectonic plates caused the Pacific Ocean, that is 6 km deep in the area, to rise and fall ten metres. This energy of the falling water caused water to surge towards the east coast of Japan in the form of a tsunami at a speed of around 800km/h. The front of the wave started to slow as the water became shallower close to the coast meaning that the back of the wave caught up to the front. This increasing pressure and compression of the wave, as well the shallower water, caused the Tsunami to rise to a maximum height of 7-10 metres.

This Link Details How a Tsunami Works: https://www.youtube.com/watch?v=Wx9vPv-T51I

Effects of the Event:

The Disaster:

Japan is a country known for large earthquakes and so have in place early warning system as well as Earthquake resistant buildings. When the earthquake first struck at 2:46pm, alerts were sent to mobile phones of everyone in the country alerting them of an earthquake. In addition to this broadcast, warnings were sent across television and transport lines and factories in Japan were shut down. The warnings worked most buildings were still standing though it was the Tsunami that caused the real disaster. This early warning system would have been the best warning for the Tsunami that was to follow as education in the country had warned people that a tsunami could follow after an earthquake. The earthquake itself didn’t claim the lives of anyone though the Tsunami that followed rocked the east coast of Japan in devastating fashion claiming a total of 15,891 lives (confirmed) with 2,500 still missing and presumed dead in 2015.

As the wave moved inland it picked up subsided land, cars, boats and anything in its way, picking up people in the debris. The prefectures of Fukushima, Ibraki, Chiba, Miyagi and Iwate, with the cities of Ofunato, Sendai and Miyako were hit first. In Sendai the wave was able to move extremely far with one wave surging ten kilometres inland at this point, flooding the Natori River. This was due to the topography of Sendai which is flat lying agrarian land. The airport at Sendai was also struck in devastating fashion leaving people trapped in the flood waters. The tsunami was the main cause of death in the disaster and to add to the devastation of the situation, as the flood waters retreated, they carried debris and people back into the ocean causing further drowning.

Fukushima Daiichi Disaster:

The nuclear power plant at Fukushima provides 4.5 gigawatts to the local grid. Nuclear fission occurs in the reactor between Uranium which produces Iodine, Cesium, Tellruides, Krypton and Xenon, as a product of the fission, heat is produced causing water to be boiled, hence spinning turbines creating electricity. At the time of the earthquake reactors 4,5 and 6 were not operational though 1,2 and 3 were. These steps below document how the disaster occurred:

1. At the time of the earthquake external power to the nuclear plant was shut off and control rods were inserted between the uranium oxide fuels to rods to the nuclear fission
2.  The plant was prepared for such occurrences and therefore backup diesel generators kicked in spraying the reactor cores with coolant
3.  These generators were operational until a larger than expected tsunami wave exceeded the 5.6 metre seawall surrounding the reactor, causing the reactor to flood shutting down the backup diesel generators
4. Plants 1,2 and 3 only have one option using systems that turn steam to water 
5. Though the failure of these systems led to a rise in temperature and the build up of hydrogen in the reactors themselves
6. To relieve pressure from the plants steam containing radioactive elements was released
7. Though attempts to cool the reactors were in vein as an explosions occurred in reactors 1,2 and 3
8.  Seawater is injected to try and cool the reactors but radioactive smoke is produced from the reactor exposing kilometres of land around the reactors

Fire:

Fires were also caused by gas and oil leaks from industrial areas and home. The leak of these materials combined with sparks created by the movement movement of two metal objects against each other. As a resulted, in 165 deaths by fires. The fires were able to spread through areas by burning on combustible materials.

Effects of the Tsunami:

Damage to Property:

The earthquake, due to Japans effective infrastructure, did little to the nation apart from damaging older buildings. The real damage came from the Tsunami that hit. The Tsunami reached heights of 7-10 metres and travelled up to 10km inland at Sendai reaching the Natori River in the area of Sendai. The waves damage to property was catastrophic. The waves initial impact caused the destruction of 300,000 buildings with another million damaged which resulted in 25 million tonnes of debris. In addition to this the main prefectures of Miyagi, Iwate and Fukushima had large expanses of agrarian land. In total 236 square kilometres of agrarian land was damaged. The black sludge in combination with debris that covered the land after the Tsunami had a high concentration of sodium chloride in it from the ocean. This salt infiltrated the surface of the ground. The prefectures that were hit by the Tsunami contain large amounts of rice paddies and are also the top producers of rice. Fortunately, the damage only resulted in damage to around 3% of rice production. The affects therefore were on a local level more than a global scale. The subsistence farmers of the area have been greatly affected as rice is a salt sensitive plant and reports have shown decreasing in production to the area from 2010 to 2011.

The Fukushima Daiichi Nuclear Power Plant also had catastrophic impacts to property and the lives of people. An area of around 800 square kilometres was sanctioned dangerous to human habitation and uninhabitable. The precise value of the cities, towns, agricultural land, homes and property lost within the radiation zone was roughly 345 to 690 billion dollars (all figures are in Australian dollars as of 22 Nov. 15)

Damage to Services: 

In addition to the houses that were damaged services were also damaged by the Tsunami. Over 4000 roads, 78 bridges and 29 railways were damaged by the Tsunami, earthquake or fires though the major costs to services came in industry. The Tsunami, apart from damaging and destroying buildings, also damaged the Fukushima Daiichi Nuclear Power Plant. This plant provided power to the local grid and with this power plant out of action, blackouts occurred frequently, which caused a drop in production in the area. The area mainly made automobiles and electrical parts and it took until late summer to make a profit again and January 2012 to reach the levels of production and growth that occurred before the Tsunami.

Financial Costs:

The cost to infrastructure is believed to stand at around 181 billion dollars. Though the rebuild is going to be far more than this with Japan needing to employ and pay for workers for the clean up of both debris and radioactive contamination, as well as guards to sanction the zones that have been deemed uninhabitable due to the radioactive fallout. The initial report was that the expenses related to the disaster would cost around 250 billion dollars though it is believed that the expenditure could reach a cost of around 415 billion. The costs include the creation of a new tsunami warning system as the old one had underestimated the size of the wave. This underestimation contributed to the people of coastal Japan underestimating the danger they were in. Statistics released from surveys conducted after the Tsunami suggested that in the worst hit prefectures only 58% made their way to higher ground. Along with the funding that the government injected into the disaster relief, Red Cross Japan also released a statement saying that they had received 1.4 billion dollars in donations. The costs of the rebuild were extensive, though the meltdown of Fukushima made the situation worse. The repair and containment of the area is estimated to cost 145 billion dollars.

Effects to Humans: 

Japan at the time had effective infrastructure and services to warn of earthquakes, as they experience earthquakes often due to the convergent boundary that run off along the entire island of Japan. Therefore, the earthquake didn’t actually kill anyone but it was the resulting Tsunami that did the damage. The official death toll stands at 15,891, 6023 injured and 2,500 people still missing and presumed dead. In addition to this 230,000 are still displaced. The majority of deaths were caused by the Tsunami though some were caused by fires that were caused by leaked gas and oil and sparks being created by the contact of two metal objects. The fire was then able spread on combustible materials killing a believed total of 165 people. In addition to this there has been further impacts due to the fallout from the Fukushima Daiichi Nuclear Power Plant which caused the displacement of 170,000 people. The Cesium that was released from the nuclear power plant has a half life of 30 years and because it takes 10 half-lives’ before it is stable, it will remain dangerous for around three centuries. The Cesium that was released inundated the ecosystem and quickly spread and contaminated water, soil, plants and animals. It has been detected in Japanese foodstuffs such as spinach, tea leaves, milk and beef, and freshwater fish up to 200 miles from Fukushima. It has been able to bio-accumulate, bio-concentrate and bio-magnify as it moves through the food chain. It is shown that the continual ingestion of Cesium can result in bioaccumulation in the heart and endocrine tissues as well as kidneys, small intestines, pancreas, spleen and liver. The impacts of the fallout are now being seen as children are being diagnosed with thyroid cancer at 20-50 times the rate than elsewhere that was not affected by the fallout. Of the 370,000 children that have been checked by an ultrasound, 137 of them have been suspected or confirmed to have thyroid cancer. We can see therefore that the tectonic disaster has had repercussions that are still prevalent today.