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2014年12月25日 (木)

地震予測地図 日本中どこでも災害は起きる

The Yomiuri Shimbun
Major earthquake disasters could strike anywhere in the nation
地震予測地図 日本中どこでも災害は起きる

What is the probability of a major earthquake striking each part of the nation?

The government’s Headquarters for Earthquake Research Promotion has unveiled its 2014 version of a geographical forecast for massive quakes nationwide, a color-coded map based on the most up-to-date knowledge and expertise gained through the study of seismic activity in all parts of the country.

The map uses a certain color to indicate the degree of earthquake risk in each area. A glance at the map shows us that no region in this nation is free from the risk of seismic disaster. The map is another sharp reminder that Japan is one of the world’s most earthquake-prone archipelagoes.

With this in mind, it is important to utilize the map as a tool for devising measures to reduce earthquake disaster damage in each part of the county.

One of the stark forecasts given by the map is the probability that a quake registering lower 6 or higher on the Japanese seismic intensity scale of 7 — an earthquake that can destroy some buildings with low quake resistance — will strike within 30 years. The data in question shows that no further delay may be permitted in taking necessary measures.

A case in point is the likelihood that a quake with an intensity of lower 6 or higher will take place around city government buildings in any of the nation’s prefectural capitals. The probability stands at an overwhelming 78 percent in Yokohama, followed by Chiba at an also significant 73 percent, and Mito and Kochi both at 70 percent. The figure for the Tokyo metropolitan government building complex is 46 percent.

Contributing to a higher probability of strong seismic vibrations originating in the Kanto region is a massive earthquake feared to hit an area along the Sagami Trough, which extends from Sagami Bay to waters off the Boso Peninsula.

Despite the urgent need for measures to cope with the situation, some municipal governments have not done enough to improve the earthquake resistance of their buildings. This is disconcerting because these facilities will be used as centers for disaster management in the event of a major earthquake.

These buildings include the Yokohama city government office, which was built more than 50 years ago. There are concerns about its state of deterioration.

We hope all local governments will study the latest seismic prediction map and make steady progress in ensuring their communities can better resist the impact of powerful earthquakes.

Bitter lesson

A similar map was drawn up for the first time in 2005. It has been updated each year to accommodate new findings from the government’s earthquake research. The map has often been used for various purposes, including the calculation of strength for architectural design and the assessment of premium rates for earthquake insurance.

However, the 2010 version of the map incorporated little data needed to predict a quake comparable to the Great East Japan Earthquake, which occurred the following year.

With this bitter lesson in mind, the earthquake research headquarters fundamentally revamped its forecasting method. In 2012 and 2013, the organ put together tentative versions of the prediction map. Its latest version contains all findings from its seismic investigation.

In producing the latest version, the headquarters expanded the scope of the areas with estimated epicenters while also extending the scales for predicted quakes. This resulted in great increases in the perceived probability of a major earthquake striking some areas, including Saitama. The figure for the city marked a 21-point increase to 51 percent.

The previous prediction maps were criticized by some as too technically difficult to understand. With this in mind, the headquarters has released pertinent information on its website, hoping to give detailed instructions on how to use the latest version of its prediction map.

The latest map also provides data related to what kind of quake is feared to hit each region, including one with its focus just below an urban populated area and another with a gigantic earthquake originating from the coastal seabed.

A look at the map provides anyone with data on the degree of vibration originating from a strong quake in an area 250 meters square. To protect one’s life, each person should take necessary steps. Measures include making houses quake-resistant and fitting furniture items with safety devices that prevent them from tipping over.

Next year marks the 20th anniversary of the Great Hanshin Earthquake. Prior to the quake, it was said no major quake would strike the Kansai area. This caused delays in improving the quake resistance of local houses and other buildings.

In this respect, unpreparedness is our greatest enemy.

(From The Yomiuri Shimbun, Dec. 24, 2014)Speech


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