Reasoning for consistent Earthquakes

The quantity of earthquakes that Japan experiences is due to the location of the islands. Japan sits on multiple continental and oceanic plates. The number of plates also contribute to the large amount of volcanoes and hot springs on the islands. If the earthquakes occur near the ocean there is then the possibility of a subsequent tsunami, which was the case on March 11, 2011.


Historical Earthquakes: 

• The Great Kanto Earthquake in 1923: hit both Kanto and Tokyo, resulted in over 100, 000 deaths

• Southern Hyogo Earthquake or Great Hanshin Earthquake in 1995 an eathquake hit and killed 6,000 people while injuring another 415,000.  

Northern Japan sits right on the tip of the west edge of the North American plate. The area where the North American Plate and the Pacific plate meet is called the Japan Trench. The Earthquake on March 11th was a result of the Pacific Plat faulting underneath the North American Plate. The push of the North American plate upwards created a huge amount of energy and water to be forces upwards, creating the tsunami. The energy from this radiates and sends waves traveling at high speed.The collision occurred 17 miles below the earth's surface.
This link gives a very clear overview, step by step as to what caused the earthquake and tsunami. 

The Ring of Fire: 
 The ring of fire is located around the pacific basin in a 40 000km semicircle. The ring of fire consists of 452 volcanoes, which is about 75% of the world's both active and dormant volcanoes. Close to 90% of the world's earthquakes occur in the ring of fire as a result of the high number of continental and oceanic plates. The consistent volcanic and earthquake action was noticed even before the plate tectonic theory was accepted. The Ring of fire is referred to as a subduction zone. A huge amount of energy is created by the movement of the plates, which explains the amount of volcanoes in the area. 
An article from about.com clearly explains each plate and its responsibility. 

"This is a listing of major volcanic areas in the Ring of Fire:

• In South America the Nazca plate is colliding with the South American plate. This has created the Andes and volcanoes such as Cotopaxi and Azul.
• In Central America, the tiny Cocos plate is crashing into the North American plate and is therefore responsible for the Mexican volcanoes of Popocatepetl and Paricutun (which rose up from a cornfield in 1943 and became a instant mountains).
• Between Northern California and British Columbia, the Pacific, Juan de Fuca, and Gorda plates have built the Cascades and the infamous Mount Saint Helens, which erupted in 1980.
• Alaska's Aleutian Islands are growing as the Pacific plate hits the North American plate. The deep Aleutian Trench has been created at the subduction zone with a maximum depth of 25,194 feet (7679 meters).
• From Russia's Kamchatka Peninsula to Japan, the subduction of the Pacific plate under the Eurasian plate is responsible for Japanese islands and volcanoes (such as Mt. Fuji).
• The final section of the Ring of Fire exists where the Indo-Australian plate subducts under the Pacific plate and has created volcanoes in the New Guinea and Micronesian areas. Near New Zealand, the Pacific Plate slides under the Indo-Australian plate."

The cause of the March 11th Earth quake:

 
Subduction: is the result of a more dense plate forcing another plate up by moving beneath it. 



















http://geography.about.com/cs/earthquakes/a/ringoffire.htm

Clarification

Sorry should clarify that posts by Group4=Kaira

Thanks

The earthquake and it's effect on mining

Mining

The above picture shows the mining areas affected by the earthquake.

Many of Japan’s industries were affected by the earthquake and tsunami, the mining industry being one of those that suffered. Japan produces nearly one quarter of the world’s iodine supply and is the second leading iodine producer in the world. Japan has many other plants other than iodine, such as cement, iron, steel, limestone, copper and more. Many of these plants were physically affected by the earthquake and tsunami. In the area that was affected by the earthquake and tsunami, there were 8 iodine plants as well as 9 cement plants. The mining industry was not only affected by the physical impacts to the mines themselves, but also on the surrounding infrastructure that supported the mining. Many large sectors of Japan experienced a loss in electrical power as a result of the natural events. Many mines which required vast amounts of electricity had no way to operate after the earthquake, and even if they were not physically affected, they had to stop operations. Many of the operable mines have lost the ability to transport their minerals as a result of many roads and highways being destroyed. Because of all of these factors, their supply of iodine has been greatly reduced.



Why is this significant?

This is very important because iodine pills are used to aid people who have been exposed to radiation. Many Japanese workers, civilians, and foreign civilians have been exposed to radiation and may benefit from taking iodine pills. The human thyroid needs and uses iodine to produce a thyroid hormone. When exposed to radiation, the radioactive iodine enters the thyroid where in concentrates and emits radiation. This greatly and in some cases inevitably cause thyroid cancer. The way that iodine pills work is that they force the thyroid to absorb all the iodine it needs from the pills and therefore will not absorb as much radioactive iodine from the atmosphere. The British Embassy began distributing iodine tablets to British citizens in Tokyo and Sendai near the end of March. Another BBC article states that the sale of iodine pills had “surged” in the United States. Many people may be sending iodine pills over to Japan including American companies sending pills to their employees in Japan. The increase in demand may not be supported by the supply, because a large percentage of the world’s iodine was based in Japan.



Sources

http://www.bbc.co.uk/news/uk-12794541

http://www.bbc.co.uk/news/world-us-canada-12765401

http://www.usgs.gov/newsroom/article_pf.asp?ID=2738

http://pubs.usgs.gov/of/2011/1069/

The earthquake and the effect on the rotation of the earth

The earthquake

The earthquake that took place was a result of subductive plates. The Pacific plate was being subducted beneath the Okhotsk plate. (A subplate of the North-American plate) The Pacific plate moves at a speed of 9 cm per year, which is relatively fast for a tectonic plate. As a result of this subduction the island of Japan shifted approximately 8 feet in certain areas. (According to Dr. Daniel McNamara-seismologist for U.S. Geological Survey) The subduction of the Pacific plate also shifted part of the earth’s mass closer to the center of the earth, as one plate slid under the other. This changed the distribution of mass and therefore affects the inertia of the earth. As the mass moves towards the center the angular momentum increases and the earth turns a little bit faster. The earthquake in Japan caused the days to shorten by approximately 1.8 microseconds. This shortening shouldn’t have any noticeable effect as it is so minute. An average year usually varies by about 1000 microseconds due to other mass distributions. There have also been other earthquakes that have had the same effect of shortening the year. The 2010 earthquake in Chile (8.8) shortened the day by 1.26 microseconds. The 2004 earthquake in Sumatra (9.1) shortened the day by 6.8 microseconds.



Sources

http://www.guardian.co.uk/world/2011/mar/11/japan-earthquake-tsunami-questions-answers

http://www.huffingtonpost.com/2011/03/12/japan-earthquake-axis-shift-climate-change_n_834985.html

http://www.cbsnews.com/stories/2011/03/13/scitech/main20042590.shtml

http://www.nasa.gov/topics/earth/features/japanquake/earth20110314.htm

Myriad other effects.

Be forewarned, this post is just a medley of tidbits of (semi-)related information about the physical and ecological effects of the earthquake.

i. (summarized from this article)

While investigation into the impact of the earthquake and tsunami has primarily focused on the effects on humans, there have been some research conducted on the effects on animals and ecosystems.

In terms of zoos and aquariums, some "were suffering shortages of gas, heater fuel, and food and drinkable water for humans as well as for animals", while others have made plans to relocate their charges elsewhere temporarily.

Interestingly enough, the biggest impact on wildlife might not be present on the Japanese mainland itself, but could be diffused throughout the small islands of the Pacific, where, in fact, the majority of wildlife-related news have come. In particular, a research station on the island of Midway has been busy conducting experiments, collecting data and monitoring the situation, both through the media and their own observations. Pete Leary, a wildlife biologist, describes,

"we passed thousands of albatross adults and petrels that had been washed into the water and lost their ability to stay dry. Their feathers were messed up by being tumbled over the island and through the vegetation."

In addition to that, thousands of wildlife have perished, in the same way humans do, during the onslaught of the tsunami, some even buried alive. (The US Fish and Wildlife Service is now estimating that the Midway Atoll National Wildlife Refuge sustained losses of over 110,000 Laysan Albatross chicks, around 22% of the total number of chicks born this year, along with 2000 adults.)

Beyond that, coral reefs and other coastal habitats have been hard hit by the inundation of saltwater during the tsunami. Indeed, soil salinization is often an issue for areas hit by tsunami; given that plants and animals are generally adapted for specific habitats (or niches within those habitats), changes in salinity or soil pH can seriously affect the survival of certain species.

On the other hand, there are some positive effects of natural disasters like tsunamis. In some cases, the silt and sediment washed inland by the waves results in coastal areas becoming more shallow, hence creating more habitats for seabirds. Decaying material (both carried by the waves and from the organisms which perished during the tsunami) could encourage the growth of plants and animals by enriching the soil.

This article used data from the 2005 Aceh tsunami in Indonesia to supplement the sparse amount of research currently available on the Honshu earthquake. This illustrates the possibility of cross-referencing investigations and extrapolating findings regarding new situations based on old ones where information might be more available. This implies too that accurate and consistent record-keeping is extremely important for scientific studies, given the empirical nature of science.

ii. (taken from this article)

In terms of other physical changes, according to the U.S. Geological Survey, the disaster left "a huge rupture in the sea floor, 217-miles long and 50 miles wide." Japan's coast has also been altered a distance of between 8 to 13 feet, along a 300-mile stretch.

More interestingly, however, the elevation of the country's terrain has actually decreased as well, and as a result, parts of it will remain permanently under sea-level. The immediate repercussion of this is that flooding might be a permanent feature of many of the current cities, as the change in altitude prevents the usual receding of the seawater.

iii.

For the more visual among us, The New York Times has an amazing page with compilations of satellite photos of the Japanese landscape before and after the tsunami.

As promised.

Here are the links I promised in the previous post.

The first one, here, is from the New York Times and provides the most comprehensive data I have seen thus far.

The second interactive map is provided by CBC and also proves useful to see the extent of the damage that was done on the whole east coast of Japan, many hundred miles of coastline.

Soil Liquefaction

While I was doing some general research on the earthquake's impact on Japan's (and affected areas') landscape, I came across this unfamiliar concept: soil liquefaction.

"Agence France-Presse reportsthat the parking lot at the Tokyo Disneyland theme park was covered with "water-logged segments from the ground." At first, officials blamed the tsunami, until they realized that the soil itself had turned to liquid. (The Tokyo Disneyland site was a setup for soil liquefaction for two reasons: it is located in Tokyo Bay, and it is built atop a landfill. Both of these are associated with water-logged soils."
(from here)

I then Youtubed it, and found several fascinating videos of soil liquefaction actually happening in real time in the aftermath of the earthquake.

This is a video of the impact of the tremors in the Chiba prefecture in Japan. The other one can be viewed here (unfortunately, embedding has been disabled, which means I can't put it here).

So, what exactly is soil liquefaction and how does it occur? As the name suggests, soil liquefaction is essentially soil suddenly developing the consistency and nature of a liquid, or in other words, 'liquifying'. More technically,

"[l]iquefaction is a phenomenon in which the strength and stiffness of a soil is reduced by earthquake shaking or other rapid loading ... [i]t occurs in saturated [completely filled with water] soils ... [w]hen liquefaction occurs, the strength of the soil decreases and the ability of a soil deposit to support foundations for buildings and bridges is reduced ..."
(from Wikipedia, the world's most trusted source!)

This phenomenon is most likely to occur in saturated, loose (i.e. low density) sandy soils, since it has a greater tendency to compress when weight is applied, as opposed to denser sands, which tend to expand in volume. When the soil is saturated by water, the gaps between soil grains are filled, resulting in the water increasing in pressure. Since water flows from zones of high pressure to low pressure, it usually moves upwards through the soil towards the ground surface. However, if the weight is rapidly applied and/or significantly large and/or repeated often (in this case specifically, by multiple, successive tremors), the water is unable to flow out in time and pressure builds to such an extent that the soil structure is lost. With that loss the strength and integrity of the soil disappear as well, and it is observed to behave like a liquid.

This is a computer simulation of soil behaviour as it becomes more and more saturated.

This is a result of the 1964 Nigata earthquake, where whole buildings have tilted or outright toppled over due to soil liquefaction.

In the case of Japan, soil liquefaction manifested itself chiefly through land instability - the cracking and movement of the ground, particularly evident through the fractures and ruptures in pavements and roads. This also had, unsurprisingly, the effect of tilting or even toppling some buildings; those gave way after the foundations on which they stood lost the soil structure necessary to support the weight of the buildings. Given the intricate physics and architecture behind the construction of such buildings, soil liquefaction often renders the buildings utterly unserviceable and uninhabitable, if not outright dangerous.

This is a picture of some of the effects of soil liquefaction in various prefectures in Japan.

Soil liquefaction predominantly happens in coastal areas or areas where the land had previously been reclaimed due to their susceptibility to flooding. On that note, soil liquefaction is different from flooding primarily because flooding occurs on the ground surface, and though water is eventually absorbed downwards by the soil, the rate at which it happens is slow enough that the soil is never saturated, and there is no build-up of pressure. Soil liquefaction occurs only when the soil is engulfed, almost, by water, from under or within, and it happens with such speed and violence that it is unable to seep upwards out of the soil in time. This definitely affects the physical landscape of the area given the havoc it wreaks on both the natural and manmade landscapes.

This article illustrates an example of soil liquefaction occuring in Aiba, an inland city, again in Chiba prefecture. Due to the tilting or sinking of buildings into the soil, soil liquefaction "has rendered over 100 homes uninhabitable", though "the damage was mostly confined to one neighborhood". The reason for soil liquefaction in this city was discovered by the city authorities, who found out from aerial photographs taken 62 years ago that the area on which the city stood was once a pond/marsh, later filled in with soil. This reclamation explains the occurrence of soil liquefaction.

One positive aspect of soil liquefaction, however, is the tendency for subsequent earthquakes or tremors to be significantly dampened and hence mitigated. Given the advance of technology, there have been methods invented to mitigate the effects of soil liquefaction, all of which are essentially based on various techniques of soil compaction to increase the density of the soil in order to lower the chances of soil liquefaction occurring.

Paleoliquefaction or paleoseismology, the study of liquefaction features left by prehistoric earthquakes, can reveal important and significant information about such earthquakes, which occurred before any records or accurate measurements were or could be kept and taken.

Personally, I found this little-known but quite destruction side effect of earthquakes fascinating. It made me consider how the physical landscape is very much in a dynamic equilibrium, and while it is really easy to assume that the physical landscape is unchanging and permanent, simple shifts or imbalances in a factor could result in the entire equilibrium collapsing, and humans are affected because our construction, infrastructure planning (and in general civilisation!) are prepared only for one state of the physical landscape without full knowledge of possible changes or problems - until they happen. Land reclamation and the construction of buildings seem like ingenious solutions to human problems of space constraints and population increase, but they also come with flaws with regards to their interaction with possible states of nature. On a larger scale, of course, this lesson can be extended to the presence of nuclear facilities within Japan, given the knowledge that Japan is a disaster-prone country. In situations like this, human technology and knowledge always seem to be running damage control.