August 28, 2014(Mainichi Japan)
Editorial: Step up efforts to take countermeasures against Sea of Japan tsunami
社説:日本海側の津波　避難と減災に本腰を

A panel of experts set up by the Land, Infrastructure, Transport and Tourism Ministry has announced estimates on the height of tsunami generated by major earthquakes that could occur in faults below the Sea of Japan.
国土交通省の有識者検討会が、日本海の海底断層で発生する大規模地震に伴う予想津波高を公表した。

Up to 23-meter-high tsunami are expected to hit Setana, Hokkaido, while five- to 12-meter-high tsunami are estimated in areas along the eastern to northeastern Sea of Japan coast from Hokkaido to Fukui Prefecture. Some three- to four-meter-high tsunami could hit areas along the western Sea of Japan coast from Kyoto Prefecture to Kyushu.
北海道せたな町で最大２３メートルが予想され、北海道から福井の日本海沿岸の高いところで５〜１２メートル、京都から九州北部の高いところで３〜４メートルの津波高になるとの予測が出た。

Although experts do not think there is a seismic source in the Sea of Japan that could trigger a huge temblor, like the Nankai Trough in the Pacific Ocean south of the Japanese archipelago, earthquakes whose focal points are situated on the bottom of the Sea of Japan are estimated to cause higher tsunami despite their smaller seismic scales.
南海トラフのような巨大地震を引き起こす大規模な震源域は日本海側にはないとみられるが、地震の規模の割に津波が高くなるのが特徴だ。

National and local governments are slow to work out countermeasures against Sea of Japan earthquakes as compared with responses to possible temblors in the Pacific Ocean. This is the first time that the national government has estimated the height of tsunami in each municipality along the Sea of Japan coast. By fully utilizing the estimates, the national government and local bodies concerned should take all possible measures to protect residents and their neighborhoods along the Sea of Japan coast from tsunami.
日本海側の津波対策は、太平洋側に比べて総じて遅れている。日本海に面した市町村ごとの国による津波予測は今回が初めてだ。これを生かし、政府と関係自治体が協力して津波対策に万全を期したい。

Massive tsunami that caused casualties have hit areas along the Sea of Japan coast in the past. The magnitude-7.7 central Sea of Japan earthquake in 1983 caused a tsunami that killed about 100 people, while a tsunami generated by a temblor with a magnitude of 7.8 in the southwest off Hokkaido in 1993 left 230 people dead or missing.
日本海側でも大きな人的被害を伴う津波が起きている。１９８３年の日本海中部地震では津波による死者が１００人に上り、９３年の北海道南西沖地震でも２３０人の死者と行方不明者が出た。

However, there are far fewer records of earthquakes in the Sea of Japan than those in the Pacific Ocean and little progress has been made on a geological survey on the seabed of the Sea of Japan. Legislation aimed at encouraging local bodies to step up countermeasures against tsunami, which came into effect following the March 2011 Great East Japan Earthquake and tsunami, requires prefectural governments to estimate the areas that are likely to be submerged by tsunami. However, prefectural governments have previously struggled to make estimates due to a lack of specific assessments of earthquake and tsunami on the Sea of Japan coast. As such, the panel of experts recently conducted analyses.
だが、日本海側は太平洋側に比べて歴史記録が少なく、地質調査も進んでいなかった。東日本大震災の後に、津波対策強化のために作られた「津波防災地域づくり法」は、津波が陸地のどこまでくるか浸水想定を都道府県が策定するよう定める。だが、日本海側での地震や津波の予測モデルがなかったため、昨年１月から検討会で分析を進めてきた。

Based on data on past earthquakes and the crustal structure, the panel reportedly examined 60 underwater faults from Hokkaido to Nagasaki, assumed that these faults could trigger magnitude-6.8 to 7.9 temblors and then estimated the height of tsunami that could be generated by such quakes.
過去の地震や地殻構造のデータなどを基に北海道から長崎沖までの６０の海底断層を選び、地震の規模はマグニチュード（Ｍ）６．８〜７．９と想定し、計算したという。

Experts say such relatively small earthquakes could trigger higher tsunami because these faults below the seabed of the Sea of Japan are relatively shallow. Since the faults are close to the archipelago, tsunami generated by earthquakes occurring in these faults could reach the archipelago in a short period of time. The panel estimates that tsunami waves could hit some areas within a minute after a quake, and that at least 30-centimeter-high waves, which could sweep away people, might hit 82 municipalities within 10 minutes.
地震の規模の割に津波が高いのは、震源となる海底の断層が浅いためだ。断層の位置も陸地に近く、短時間で津波が到達する。一部地域は地震発生から１分以内に津波が到達し、半数近くの８２市町村で、人が流される恐れのある高さ３０センチの津波が１０分以内に到達する可能性がある。

Based on these estimates, prefectural and municipal governments in areas along the Sea of Japan coast are required to review their disaster-prevention plans. Top priority should be placed on safely evacuating local residents.
今回の予測を受け、道府県や市町村は防災計画を見直す。最優先は、住民の安全な避難だ。

A panel of experts within the government's Central Disaster Management Council recommended in September 2011 that all regions be rebuilt to make sure that residents can walk to safe locations within about five minutes after tsunami hit.
中央防災会議の専門調査会は２０１１年９月、津波が発生した場合、原則として歩いて５分程度で安全な場所に避難できるまちづくりを提言した。

The panel made the recommendation on the assumption that a huge earthquake could hit areas along the Pacific coast. However, similar countermeasures should be taken in areas along the Sea of Japan coast. Both national and local governments along the Sea of Japan coast should designate evacuation routes and regularly conduct evacuation drills in preparation for deadly tsunami, while implementing all possible measures to lessen damage caused by such disasters.
主に太平洋側の巨大地震を念頭に置いたものだが、日本海側でも、そうした姿勢で対策に取り組まなければならない。避難路の整備や日常的な避難訓練などの備えを進めたい。あらゆる減災の手立てを尽くすべきだ。

The panel also announced its estimates of the height of tsunami that could hit 11 nuclear power stations along the Sea of Japan coast, but the estimated figures were below those by the plant operators.
今回、日本海側にある１１の原子力発電所ごとの予想津波高も公表されたが、いずれも電力会社の想定を下回った。

Still, there is a possibility that the estimates could change as seismological research progresses. As such, it is only natural that authorities should strictly examine the safety of each nuclear plant.
それでも地震の研究が進めば、想定が変わることも十分にあり得る。厳しい目で安全審査を進めるのは当然だ。

毎日新聞　2014年08月28日　02時40分