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Wednesday, September 11, 2013

earthquakes

September 1st is Disaster Prevention Day. The day was established to mark the Great Kanto Earthquake which occurred at 11:58:44 am Japan time on September 1, 1923. August 30 to September 5 (the first week of September) was the Disaster Prevention this year.

Japan Tourism Agency provides emergency information to foreign tourists visiting Japan on the following site.

safety tips for travelers(English version only):
http://www.jnto.go.jp/safety-tips/pc/index.html


More than 105,000 people were left dead or missing by the 1923 Great Kanto earthquake.
About 90% of the victims burned to death.  In Tokyo City at that time, the coincidence of 134 fires produced a large firestorm, and a produced gigantic fire whirl killed 38,000 people who evacuated to the site of a former army garment factory.  In contrast, 20,000 people who evacuated to the Fukagawa Villa of the Iwasaki family were safe. The villa became open to local people as an evacuation spot after the quake. The factory site was a vacant lot, but the villa had many trees, shrubs, and a pond. More than 40% of the city's total land area was burned.

Yamashita Park in Yokohama was made in 1930 out of reclaimed land made from the rubble caused by the Great Kanto Earthquake in 1923. In this August, boring survey was conducted at the park in order to investigate the circumstances at the time. Discovered debris including broken pieces of roof tiles, bricks, bowls will be opened to the public at Yokohama Port Museum next to Sail Training Ship Nippon Maru from September 28 to November 17.

Annual comprehensive disaster prevention drills were held on September 1. The prime minister took part in the drills together with all Cabinet members. Although 1,330,000 people in 43 prefectures were scheduled to participate in the drills, they were cancelled due to torrential rains in Kyushu and Shikoku.

The drills had countermeasures for the Nankai Trough Earthquakes(the Nankai megathrust earthquakes). Japan has 60-70% chance of a magnitude 8-9 earthquake along the Nankai Trough which extends about 770 km from Suruga Bay off Shizuoka Prefecture to areas off eastern Kyushu. The trough have caused magnitude 8 earthquakes regularly with an interval of 100 to 200 years.  It is estimated that some of these earthquakes were caused by the movement of several faults at the same time. It's been estimated that if some groups of the hypocentral region move at the same time, a megaquake will result in 230,000 deaths from tsunami, 82,000 from building collapse, 10,000 from fire.

Long-period earthquake ground motion is also a big problem. Buildings on the soft ground entered into resonance with an long-period earthquake. The 2011 Tohoku earthquake damaged a building in Osaka far away from Tohoku. High-rise buildings tend to shake on the soft ground, and low-rise buildings tend to shake on the firm ground. Upper floors of high-rise buildings shake badly.


Although we have made repeated attempts to minimize earthquake damage, earthquakes often exceed all expectations and baffle our calculations. Every damage from the past earthquakes raised new problems.

Seismic hazard assessment became valued more than earthquake prediction after the 2011 Tohoku earthquake in Japan.

Postseismic deformation of the 2011 Tohoku earthquake have influenced volcanos and active faults in other areas.  Global positioning system (GPS) equipment can detect sub-centimetre changes in land movements. Experts have scoured past earthquake data. Geologists have analyzed tsunami sediments discovered in strata and the remains.

A slow slip event(slow earthquake) is a discontinuous, earthquake-like event that releases energy over a period of hours to months. Some seismologists think monitoring the changes of slip patterns could help in earthquake prediction. However, A linkage between the changes of slip patterns and major earthquakes cannot be unproved for now. Changes in well-water levels are seen by some as a portent of a major earthquake.

Hinako Sugiura(杉浦日向子, 1958-2005) said in her comic book "YASUJI Tokyo" written in 1988.
"It would appear to me that Tokyo is ready to return to a wilderness at any moment.
Even if Tokyo is flattened by a large earthquake or the whole Tokyo area is exposed to radiation, we would never think that is a dream then. We dream on the wilderness till then.
The wilderness makes us dream."

Tokyo(Edo) was repeatedly destroyed by many fires, earthquakes and air raids. A fire whirl is possible even now. The coincidence of fires could block escape route. Seismic retrofitting costs a great deal of money. Not all of communities can afford to take adequate measures. It is inevitable that fires will occur in densely built-up wooden housing areas in Tokyo and another cities. The 1995 Kobe earthquake caused fires in densely built-up wooden housing areas.

I thought it was not my turn on March 11, 2011 when the Great East Japan Earthquake occurred. However, the next megaquake might hit my area. Nowhere in the Japanese islands is quake-free. My aunt and her family experienced the 1995 Great Hanshin-Awaji Earthquake in Kobe,  and my cousin and his family did the 2011 Great East Japan Earthquake in Miyagi.

Earthquake occurrence is nobody's fault. If one day suddenly we lost all things due to an earthquake, there's no one to take revenge on. We just have to accept our fates with resignation then. However, those involved in shoddy construction were accused in court after the Great Hanshin-Awaji Earthquake. Some family members of tsunami victims are accusing companies, schools of having neglected their duty to ensure the safety of the victims.

Tainted water leaking from tanks at the Fukushima Daiichi nuclear plant is a big thing to worry about right now. Some people said the government should give preference to the problem of tainted water over hosting the Olympics. Some said the holding of the Olympics leads to benefits for disaster areas because the world keeps strict watch on the problem until the 2020 Tokyo Olympics. I fear that only Tokyo flourishes and disaster areas are left behind.

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