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Fukuoka Quake 2005 – Revisited

Oct 24, 2011 19:07 没有评论

On the anniversary of the biggest earthquake to hit Fukuoka in 200 years, we look back and offer tips for preparedness.

Written by: Arash J.Gandomi
Student of Seismology at Kyushu University

I’m from Iran and I have experienced several earthquakes, both in Iran and Japan, ranging from minor to big and dangerous. I came to Japan around two and a half years ago. I’m very glad to have the opportunity to study seismology in Japan since it is one of the world’s leading centers of expertise on this subject.
Fukuoka’s Seismicity Revealed
The Kego fault line runs right through the middle of Tenjin in Fukuoka. And yet, in seismological terms, the area has been relatively quiet over the last couple of centuries. This makes it difficult to answer people’s questions about the safety of Fukuoka with regards to earthquakes. But, last year on March 20 the question was kindly answered. ‘Why kindly?’ you may ask. Before answering that, let me briefly explain what happened last year on March 20 in Fukuoka.

A Quiet Sunday…
It was about 10:55 Sunday and I was still in my bed, perhaps the same as many of you. Suddenly, I noticed my TV moving around on its shelf. I thought I was dreaming, but then I realized it was not only my TV; everything was shaking and getting stronger with each moment. As it got stronger, my education kicked in and I realized so far, I had felt P-waves, or primary waves – the first wave types released from a fault during an earthquake. Since they travel faster than other types of waves, they arrive first. So, you feel P-waves, then, depending on your distance from the source of the earthquake you will have a few seconds to prepare for the S-waves which are much stronger and more destructive. I call these seconds between the arrival of P and S waves the ‘last chance.’ And believe me, it really can be the last chance in some cases. Later in this article I’ll let you know what you can do during this time. Many earthquake early warning systems are based on this fact that less destructive P-waves arrive first. Some earthquake-resistant buildings are set up so that as soon as the P-waves are detected, the warning system of the building is activated.

Studying the Quake
The source of last March’s earthquake was estimated to be about 30km off the west Fukuoka coast in the Genkai sea, near Genkai Island. Its magnitude was 7.0 on the Richter scale. The fault that was the source of the quake was found through the study of aftershocks by Kyushu University Seismological and Volcanological Observatory (SEVO). The fault seems to follow the same trend as the Kego fault that passes trough Tenjin but extends into the sea. This is one of the reasons why I said earlier that our question about Fukuoka’s seismicity has been answered kindly. For seismologists, this terrible event contained much useful information. If the quake had happened on the land extension of the Kego fault, the damage could have been many times worse.

The Damage Done
During this earthquake one person died and about 50 were seriously injured. Several hundred people were injured to some degree, and around 300 buildings suffered varying degrees of damage. Genkai Island was particularly badly affected due to its proximity to the source and the older, traditional Japanese houses that are less resistant to shaking than engineer-built ‘mansions’. In Genkai Island about 120 houses were destroyed and 55 others partially damaged. In Fukuoka City too, traditional Japanese houses, particularly in the areas of Daimyo and Imaizumi, were the most heavily damaged; insurance payments for damages were estimated at approximately 15.8 billion. In Tenjin, windows were shattered and concrete cracked. Temples and shrines also suffered damage. Genti Toyokuni, a student of seismology at Kyushu University, surveyed the falling stones and statues of the temples; this can be a serious problem for people visiting shrines or temples to pray for safety during an earthquake. If an earthquake happens and you are in a temple, the area around stone statues should definitely be avoided.

It is important to note in comparison that in the Kobe earthquake in 1995, about 6,500 people died. In some ways, we have been fortunate in Fukuoka that we didn’t suffer so much. Furthermore, that tragic death toll in Kobe occurred in Japan, one of the best prepared countries in the world against earthquake hazards. An earthquake of similar magnitude to last year’s occurred in Iran in 2003 and caused around 30,000 deaths.

Aftershocks
After the main shock of the Fukuoka earthquake, several smaller aftershocks happened around the source. An earthquake large enough to cause damage is usually followed by several aftershocks felt within the first hour. The rate of aftershocks decreases quickly; the decrease is proportional to the inverse of time since the main shock. Bigger earthquakes have more numerous and powerful aftershocks. According to my experience, the first week after an earthquake the size of Fukuoka’s is still the ‘red zone’, susceptible to strong aftershocks. However, even after two months some aftershocks could be felt, and exactly one month from the initial quake there was a very strong (6 on the Richter scale) aftershock. Sometimes before big earthquakes, moderate foreshocks happen, but in the case of the Fukuoka earthquake, no clear foreshock was reported. In the case of the Bam earthquake in Iran in 2003, foreshocks were reported the night before the earthquake but due to the lack of high-tech seismic networks, they weren’t officially noticed, unfortunately.
Predicting Earthquakes?
When people hear that I’m studying seismology, the first question they ask is about predicting earthquakes. The prediction of earthquakes has always been one of humanity’s dreams. In fact, predicting the time of an earthquake is just one side of the story and there are institutes and researchers working on this type of prediction. But, most seismologists are working on ‘strong ground motion prediction’. Strong ground motion prediction is based on investigating the existing seismological aspects and the ground condition of each place to determine what would happen during future earthquakes and what amount of shaking could be expected. Some people may think that predicting the time of an earthquake is important, and it is. However, if we know how much shaking to expect and our buildings are prepared for that, then no matter when the earthquake happens, we will be safe.

Perhaps most foreigners have heard about Japan’s seismicity. There is a ‘ring of fire’ that surrounds the Pacific Ocean and includes Japan. Seismologists refer to a Global Seismic Hazard map, showing the parts of the world at the highest risk: east and south Asia, Japan, Indonesia and surrounding areas, south-western China and north India plus Pakistan, Turkey and Iran. Eastern Europe, especially Greece and Italy, has a higher risk, too.

Seeing the damage and casualties caused by earthquakes even in prepared countries such as Japan shows us that we must always be aware of earthquakes wherever we are. Even in advanced, developed countries, we are not perfectly protected against earthquakes, so we should spare a thought for the tragic stories of earthquake disasters in developing countries.

At-a-Glance
Time: 10:53 March 20, 2005
Magnitude: 7 (Richter scale)
Official Name: Fukuoka Prefecture Western Offshore Earthquakes
Deaths: 1
Seriously injured: 50 (approx.)
Injured: Up to 1,000 (approx.)
Damaged buildings: 300 (approx.)
Most damaged area: Genkai Island.
Estimated insurance payouts: 15.8 billion
Legend has it…
Since humanity began, we’ve been concocting interesting explanations for the natural phenomena that affect us. With the benefit of hindsight, some may seem a little eccentric…

Japan
The great catfish Namazu is curled up under the sea with the islands of Japan resting on his back. The god Kashima holds a heavy stone over his head to keep him from moving. Occasionally when the god lets his guard down, the catfish is able to squirm around. This causes earthquakes.

Siberia
In Kamchatka, the god Tuli drives the sled that carries Earth. It is pulled by flea-infested dogs. When the dogs stop to scratch themselves, the Earth shakes.

America
The Gabrielino Indians believe that Earth is carried by turtles on their backs. One day after arguing, three of the turtles decided to swim east, and the others swam west. The earth shook and cracked. They couldn’t swim far because of the heavy land on their backs, so they stopped and made up. But, occasionally, the turtles that hold up the world argue again, and the earth shakes.

Peru
The ancient Maimas believed that earthquakes were caused by the footsteps of a god when he came to earth to count the number of people. Residents wanted to make his job easier and quicker, so they ran from their houses shouting ‘I’m here, I’m here!’. Going outside was a good move; the houses would often have crumbled under the force of the earthquakes.
Earthquake Trivia
– There are an estimated two earthquakes every minute around the world.
– The largest earthquake recorded was in Chile in 1960. It was 9.5 on the Richter magnitude scale, caused over 6,000 deaths and triggered a tsunami that affected people here in Japan and Hawaii.
– The earliest known earthquake detection device was invented in 132 A.D. by a Chinese philosopher. It was a large jar with a system of pendulums and carved dragon’s heads that could detect vibrations as far as 600km away.
– Earthquakes are incredibly powerful; on the Richter scale, a magnitude 4 quake will release the approximate equivalent of 1,000 tons of TNT, or a small nuclear weapon. A magnitude 9 quake will release as much energy as around 32 trillion tons of TNT.

You Should Know
There are several guides available that explain what to do before, during and after an earthquake. Everyone should find and read one of these. You can start with the one in this issue! However, I’d like to share some of my experiences and comments.

There are things that you should do before an earthquake. One of the most important is to anchor any unstable things in your home e.g. TV, ornaments, fragile things and anything on the wall. It is not difficult to find clips in the 100 Yen shops to secure your things at home. Never place heavy objects over beds, and keep heavy objects lower than the head height of the shortest member of the family. If you have a desk or table, try to keep the space beneath it empty. During an earthquake, something as simple as a desk can help so much as shelter. When buying a desk, don’t hesitate to pay a little more for a stronger one; it could save your life. Keep your bed away from windows to prevent falling broken glass and before going to sleep, close the curtains. As I said in the beginning, P-waves are the precursor of an earthquake and give you valuable seconds to prepare. It is difficult to recognize them but it is possible. P-waves’ shaking is vertical (up and down) and similar to acoustic waves. If you are near to the source you may hear a loud noise similar to an approaching airplane. Several people who live near Uminonakamichi reported hearing a very strong roaring sound during the earthquake.

During an earthquake, first of all try to stay calm. If it’s at night and you are in bed, get underneath it if possible, or cover yourself with your covers or futon. If you can, get under a strong desk or table. Remember, don’t use the stairs (or an elevator) during an earthquake. If you are in a car try to keep away from underpasses and overpasses, stop in a safe area and stay in the vehicle. Earthquakes that happen at night have more casualties because people are asleep or resting. I remember an earthquake in northern Iran that caused about 40,000 deaths in 1990. In the hospital I spoke to a boy who was the only survivor from a family of eight. He said that as soon as he felt the shaking, all he did was cover himself with his futon. During an earthquake, people are often injured by falling debris or sharp falling objects. As such, something as simple as pulling your covers over your head can help your chances of survival.

Protect Yourself!

Presented here is a snapshot of some of the earthquake-related products readily available in Japan. There are many different items on offer, and we are not recommending any one over the other. Earthquake safety is a serious business, so however you decide to prepare yourself, just make sure you do!
MUJI Bosai Survival Pack
Be prepared and stylish at the same time! Contains a water-proof radio with mobile phone charger, candles, water preservers, gloves, medical plasters, and much more.
10,500 yen at MUJI

Emergency Clothes Set
Ultra-compressed set comprising t-shirt, gloves and towel. Very small and light, comparable to the tissue packs given out on the street in size.
1,050 yen at INCUBE

Emergency Nalgene Bottle Set
Nalgene, the world’s greatest bottle-makers, offer this set complete with survival sheet, poncho, pen-knife, gauze, and more.
5,460 yen at INCUBE

Anti-Slip Pads
Perfect for stopping your furniture sliding around your faux-wood appartment floors during an earthquake. Could save in damage repair.
Medium size: 1,302 yen at INCUBE

Wind-Up Radio
Can run on batteries or mains, or wind-up in an emergency. Listen to radio for emergency broadcasts, plus recieve TV audio. Comes with built-in flashlight, too.
6,609 yen at INCUBE

Earthquake Procedures Mug
Contains (in Japanese) important things to remember to survive an earthquake. Drink from it every day and be well prepared!
630 yen at INCUBE

Pocket Stove
A top seller after last year’s quake, this mini stove cracks open to reveal a store of combustible blocks. Use during an earthquake, when gas is turned off.
945 yen at Ishii Sports

Freeze-dried Food
Long lasting, light and securely packed, freeze-dried food should always be kept on hand in case of emergency. Large variety available.
From 294 yen at Ishii Sports

Shatter Prevention
A roll of thin plastic for sticking to your windows. Prevents glass from shattering and falling everywhere during a quake.
1,029 yen at INCUBE

E-Call
An emergency whistle that is so powerful it can be heard up to 700m away. Invaluable should the unthinkable happen and you need to alert others.
567 yen at Ishii Sports
MUJI Tenjin Solaria
Solaria Plaza B1F
Tel: 733-7004 Open: 10:00-20:00 Closed: some Tue

INCUBE
Solaria Stage Bldg. 5F
Tel: 713-1092 Open: 10:00-20:00 Closed: never

Ishii Sports
Tenjin Saiwai Bldg. 1F
Tel: 737-9136 Open: 10:00-20:00 Closed: Mon.
The Fukuoka Bosai Centre

Learn Earthquake Safety and Have Fun, Too!

Don’t be fooled into thinking this place is only for kids. The Fukuoka Citizens’ Disaster Prevention Center presents useful information about disaster safety in a fun and memorable way. Education and practice is the best way to protect yourself, so try the amazing earthquake simulator: a room that shakes up to magnitude 7 on the Richter scale. There is also a typhoon-wind simulator with wind speeds up to 30m/ sec. There’s much more too – fire extinguisher training, emergency procedures training, even first aid training for groups. Visit or call for more details. The Center welcomes international visitors, and information is available in English, Korean, Chinese and French.

Fukuoka Citizens’ Disaster Prevention Center
1-3-3 Momochi-hama, Sawara-ku, Fukuoka
Tel: 847-5990
9:30-17:00
Mon., last Tue. of each month, New Years (12/28-1/4)
Free
www.fuku-bou.or.jp

Get More Information!

Fukuoka City Hall (1F)
Visit to get your Earthquake Emergency Procedures booklet in English, Korean, Chinese, Japanese and Portuguese. Located behind IMS Building in Tenjin.

Rainbow Plaza (IMS Bldg. 8F)
Carries ‘Living in Fukuoka’, a comprehensive guide for foreigners living in Fukuoka (in English, Chinese and Korean), which has a section on Earthquake safety.

Your Local Ward Offices
Some ward offices carry copies of ‘Living in Fukuoka’ and they should be able to provide you with a Welcome Pack with some useful information when you go through the Alien Registration process.

Love FM
Turn on your radio for the latest information during a disaster. Love FM (76.1 Mhz, 82.7 in Kitakyushu, 82.5 in Western Fukuoka) offers information in 10 languages. NHK (612 Khz AM, 540 Khz in Kitakyushu- search the web for full listings) offers detailed information in Japanese.

Useful Links

Kego Fault’s Recent Activity
www.hinet.bosai.go.jp/topics/FKO20050320 (J only)

Kyushu University Seismological Group
http://www.sevo.kyushu-u.ac.jp/HYPO/index-e.html

The latest earthquakes in the world:
http://earthquake.usgs.gov/eqcenter/recenteqsww/

Earthquake Research Institute of University of Tokyo
http://www.eri.u-tokyo.ac.jp/index.html

Prof. David A. Johnson’s March 2005 Quake Homepage
http://www.seinan-gu.ac.jp/~djohnson/fukuokaquake/

Fukuoka Quake 2005 – Revisited

僕の名前はアラシ・ガンドミ、九州大学の大学院で地震学を研究して2年半になる。母国イランでも日本でも地震を経験済みだ。日本の地震に関する研究は進んでいるから、ここで研究できて嬉しいよ。
××3月20日午前10時53分 ××
警固断層は市の中心部を通っている上、100年以上に及び大規模な地震の記録がなかった福岡において、地震対策は万全か？という疑問に答えるのは難しい。しかし去年3月20日、親切にもその答えが出された。それは日曜日の午前11時頃、僕はまだ眠っていた。突然テレビや棚が揺れだし、一瞬夢か？と思ったけれど、揺れが強くなっていくにつれて、この正体が、大きな地震のときに最初に感じられる弱い揺れだったのだと悟った。通常、その数秒後には強い揺れがやって来る。この数秒間は大きな揺れに備えるラストチャンスといえるだろう。実際いくつかの建物は最初の弱い揺れの直後に警報が出されるしくみになっている。
×× 震源地、警固断層？！××
3月の地震の震源は福岡の西方沖30キロ、玄界灘に浮かぶ玄界島の付近だとわかった。気象庁が発表した震源地のマグニチュードは7.0。地震を引き起こしたとされる断層は、九州大学の地震火山観測研究センターによる余震の解析で見つかった。この断層はちょうど警固断層を海側に延ばした場所にあるように見える。これが、福岡の地震対策についての疑問に「親切にも答えが出された」と言った理由である。地震学者にとってこの地震は、もし警固断層で地震が起こったらどんなにひどい被害が出るのかを予測する、良い研究材料となったのだ。警固断層で将来、地震が起きないという保障はどこにもない。
ﾊ

×× 地震の被害は…××
この地震で福岡県では1人が亡くなり、50人ほどが重症、数百人が軽症を負い、およそ300ほどの建物がダメージを受けた。特に玄界島の被害は大きく、127棟が崩れ落ち、ほか50棟ほどが損傷した。福岡市内でも大名や今泉の古い建物は損傷し、支払われた保険金の総額は158億円に及ぶと言われている。天神の街も強い揺れに襲われ、ビルの窓ガラスが割れて散らばった。古いお寺や神社の損傷もひどかった。同じ九州大学で地震学を研究している豊国源知は神社の石灯篭や鳥居の被害を調査した。結果、志賀島の志賀海神社では18基すべての灯篭が、箱崎宮でも全体の7割の47基が倒壊していることがわかった。これは地震の時にお寺や神社にいると如何に危険かを物語っている。あなたが参詣している最中に地震が起こった時は、鳥居や灯篭のそばには決して近寄ってはいけない。
×× 福岡の“安全神話”崩壊 ××
1995年の阪神・淡路大震災では6500人が亡くなったことを思うと、今回、被害の少なかった福岡は実に幸運だったと言えるかもしれない。去年の福岡の地震と同じ震度で、2003年、イランはなんと3万人の死者を出してしまったのだから。

大地震にはつきものの「余震」。今回の福岡でも主震の後、震源地を中心に余震が続いた。その数は時間が経つにつれ次第に少なくなるが、地震の規模が大きいほど、余震の数や規模も大きくなる。大規模な地震の後には1時間以内に余震が数回、僕の経験から言うと、去年の福岡の場合は地震の１週間後もまだまだ余震が続き、予断を許さない状況だったと言える。そしてちょうど1ヶ月後の4月末、マグチュード6の、余震というには大きすぎる揺れが観測されたのだった。大地震の前には前震が起こる事も多いが、福岡で起きた地震の場合には目立った前震はなかった。一方でイラン大地震では前震が前夜に観測されてはいたにも関わらず、地震対策ネットワークの欠如により公表されずに終わっていたのだ。

僕が地震を研究していると言うと大抵の人は「地震を予測するって可能なの？」と聞いてくる。これが実現できれば素晴らしい事だ。もちろん、地震予測の研究をしている学校や研究室は多くあるのだが、たいていの地震の研究ではいつ地震が起きるのかではなく、地震による地面の揺れや動きに注目している。いつ地震が起こるか、よりもどのくらいの威力で地震が起こるか、その為には建物の強度をどこまであげなければならないのかが判っていれば、大きな被害を防ぐことも可能だ。

日本が地震の多い”環太平洋火山帯”に位置していることは皆さんご存知のはずだ。特に地震の多いエリアとして東・南アジア、インドネシアと共に名を連ねている。その他、中国の南西部、北インド、パキスタン、トルコ、イランなど。もともと防災の意識の高い先進国の日本でさえも地震の被害は多く犠牲者を出しているのだから、どこにいても地震の危険性を把握しておくべき。また被害の特にひどい発展途上の国々にその情報を提供すべきだと思う。
×× 知っておくべき事 ××
では実際に地震に備える為にはどうしたらよいのか！？僕のオススメする対策はこちら。
● タンスやテレビ、また壁に掛けた装飾品などを固定する事。（100円ショップが大活躍だね）
● 重さのある物は低い位置に置くといい。
● 机の下は常に片付けておく事。ちょっとばかり贅沢をしても、丈夫なものを選ぼう！
● 窓ガラスが割れた時に備え、ベッドは窓から遠ざけておく。
● 前震が起きたら、主震に備える。

地震がおきても慌てないことが大切だ。寝ている時に地震がおきたら、布団をかぶったり、机やベッドに下に避難することだ。そしてここが肝心！決して階段を使わないこと、地震が起きると階段は危険極まりない空間へと変貌するからだ。運転中に地震を感じることは難しいが、地震に気づいたらガード下や橋の上は避け、安全な場所に駐車し車の中で地震が終わるのを待とう。4万人の死者を出した1990年のイラン地震でとある少年が助かったのは「布団をかぶったから」。ものが体に落ちてきたり、突き刺さったりする事による死傷者が多いのが地震だ。したがって布団をかぶるという単純な行為も、希望の光だと言えるだろう。
×× 学ぶことは楽しいこと××
ちびっこ用の施設？！などと軽んずるなかれ！ここ「福岡市民防災センター」ではいろいろな模擬体験を通して、もしもの時の防災の知識や対処法が学べる施設なのだ。災害から身を守るには一人一人の防災意識を高めることが必要。地震体験（震度１～７）や消火訓練、強風体験（風速30m）やクイズを通して楽しみながら防災の知識に触れる事ができる。また、同センターでは福岡市内の幼稚園、学校、町内会などのグループを対象に防災講座も行っている（無料／要予約）。
×× 地震トリピア ××
★世界では日々地震が1分間に2度起きている。
★観測史上最大の地震は1960年にチリで起きた。マグニチュード9.5を記録し、6千人以上の尊い命が奪われた。地震による津波はハワイや日本にも押し寄せたほど。
★世界初の地震計は西暦132年、中国の哲学者によって発明された。棒が倒れて地震の発生と方位を知らせる装置で、600キロ先の揺れまで観測することができた。
★地震の破壊力は絶大だ。マグニチュード4の地震はTNT1000トンまたは小さな核兵器、そしてマグニチュード9の地震はTNT32兆トンに相当するエネルギーを持っている。
×× 自然にまつわる神話 ××
世界の不思議は自然の摂理。人間だってそうなのです！てことでどんな理屈だって成り立たない時もある。各国の神話もアンビリーバボー？

■日本
ナマズが暴れると地震が起こる、と昔から言われている。鹿島大明神が大きな岩でナマズを押さえこんでいる…らしい。
■ シベリア
カムチャッカではソリを引く犬達にはノミがいて、犬が体を掻くのをやめたら地震が起こると言われている。
■ アメリカ
地球を背負っているのは実は亀！時々喧嘩をしてしまう彼らは別々方向へ泳ぎだす。これが地震を引き起こす原因、というのだが…。
■ ペルー
神様が国民を数える為に地上に降り、その足音が地震を引き起こすと言われてる。