Wednesday, September 1, 2010

Disaster Prevention Day

September 1st is Disaster Prevention Day. It was established to mark the Great Kanto Earthquake which occurred at 11:58:44 am Japan time on September 1, 1923.
Mass of the rubble of the Great Kanto Earthquake are still buried under Yamashita Park in the port of Yokohama.

This day is also the 210th day(二百十日) from the first day of spring according to the lunar calendar and it means the beginning of typhoon season.
Every year on this day, extensive emergency drills are organized throughout the country. Many train companies make their trains go slower temporarily on this day.

Earth's subsurface consists of bedrocks called plate and its movements trigger a major earthquake. Under or near Japan, there are four kinds of plates. Two plates slide towards each other, and formed subduction boundaries are accumulating strain.

Japan Geotechnical Consultant Association says that the earthquakes over magnitude 7.0 took place 900 times during the last 90 years in the world and ten percent of the earthquakes occurred under or near Japan.

In Kanto region or Shizuoka Prefecture, most schools and many large companies conduct emergency drills, and I participated in them many times. At a drill in 1995 when the Great Hanshin earthquake occurred, a drill supervisor stated flatly that a big earthquake was sure to take place. In that year, many people took part in emergency drills seriously.
I recently learned that such drills are rarely held on at the schools in other areas.

People living in Kanto region or Shizuoka Prefecture know that a big earthquake will be sure to take place in these areas.
A big earthquake can be likened to a friend's death. No one knows when that will happen and who will die first. Though we know in our heads death is sure to all, we will be overwhelmed by a sense of loss if it becomes a reality.
Earthquake occurrence is nobody's fault, so we just have to accept it when being damaged by an earthquake suddenly.

Although we have made repeated attempts to minimize earthquake damage, earthquakes often exceed all expectations and baffle our calculations. Seismic retrofitting costs a great deal of money.
Every damage from the past earthquakes raised new problems and led to amendments to the Building Standard Law that stipulates seismic capacity of buildings.

The Japan Meteorological Agency provides information on the affected areas when an earthquake with a seismic intensity of 5.0 or more is expected to take place by using Earthquake Early Warning system. However, the warning is not in time for areas close to the earthquake center.

Kogakuin University professor Youtarou Hatamura(畑村洋太郎) says that the shinkansen(bullet train) bridge piers that collapsed or damaged in the Great Hanshin earthquake and the Miyagi earthquake in 2003 led to reinforcements of the shinkansen concrete bridge piers in hazard areas. Although a Joetsu Shinkansen bullet train was derailed in The Chuetsu Earthquakes in 2004, the piers might have been broken and the elevated railroad tracks might have given way if a railroad company failed to make repairs.

Long-period earthquake ground motion is a big problem now.
Areas that have soft ground is prone to the motion. Upper floors of high-rise buildings shake badly. Buildings that enter into resonance with an long-period earthquake collapse in the quake. It was typically seen in The Mexico City earthquake in 1985.

Many people can't go home immediately an earthquake occurs in areas far from their homes.
Local governments and most large companies accumulate stockpiling of water, food, medical goods for disasters. Some local governments also provide temporary bathrooms and signed an agreement for supporting such people with convenience stores and gas stations, but public institutions fail to take sufficient measures against such people.
There are books or a drill to walk home safely in case of a disaster.
Online message boards services by mobile phone companies operate in times of disaster because many calls to confirm the safety of their families or relatives flood the phone lines.

The flexible structure of ancient towers is more resistant to earthquakes.
No tower in Buddhist temples fell down at the time of the Great Kanto Earthquake and the Great Hanshin earthquake. Horyu-ji Temple Five-storied Pagoda(法隆寺五重塔), which was built about 1300 years ago, has not been damaged at all even after nine times of severe earthquake with a Japanese seismic intensity of 5.0 or more. I heard that no tower in the temples all over Japan has ever fallen down because by earthquakes.

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