Hari Sabtu, 27 Februari 2010, terjadi gempa Chili dengan magnitude 8.8 (usgs), yang men-generated tsunami di Pacific, hingga ke Jepang, yang mendapat kiriman gelombang tsunami 1 hari sesudah gempa. Subhanallah.Tsunami Model for Chilean earthquake – Earthquake Research Institute, Tokyo
Sebelumnya pada tahun 1960, terjadi gempa mahadashyat Chili dengan magnitude 1960, yang mengenerate tsunami di Pacific, juga hingga ke Jepang, mengakibatkan banyak kerusakan dan kematian. Kawasan Pacific benar-benar belajar dari pelajaran itu, dan benar-benar mempersiapkan diri untuk kejadian masa mendatang. Terbukti, usaha mereka tidak sia-sia, tepat berselang 50 tahun, kembali Chili melepaskan gempa dashyat. Menunjukkan pentingnya usaha untuk hidup bersinergi dengan fenomena alam.
Earthquake Summary, USGS.
This earthquake occurred at the boundary between the Nazca and South American tectonic plates. The two plates are converging at a rate of 70 mm per year. The earthquake occurred as thrust-faulting on the interface between the two plates, with the Nazca plate moving down and landward below the South American plate.
Coastal Chile has a history of very large earthquakes. Since 1973, there have been 13 events of magnitude 7.0 or greater. The February 27 shock originated about 230 km north of the source region of the magnitude 9.5 earthquake of May, 1960 — the largest earthquake worldwide since the beginning of instrumental seismology at the beginning of the twentieth century. The giant 1960 earthquake spawned a tsunami that caused destruction on coasts throughout the Pacific Ocean basin. An estimated 1600 lives were lost to the 1960 earthquake and tsunami in Chile, and the 1960 tsunami took another 200 lives among Japan, Hawaii, and the Philippines. Approximately 300 km to the north of the February 27 earthquake is the source region of the magnitude 8.2 earthquake of August 17, 1906. The tsunami associated with the 1906 earthquake produced some damage in Hawaii, with reported run-up heights as great as 3.5 m. Approximately 870 km to the north of the February 27 earthquake is the source region of the magnitude 8.5 earthquake of November, 1922. The 1922 earthquake significantly impacted central Chile, killing several hundred people and causing severe property damage. The 1922 quake generated a 9-meter local tsunami that inundated the Chile coast near the town of Coquimbo; the tsunami also crossed the Pacific, washing away boats in Hilo harbor, Hawaii. The magnitude 8.8 earthquake of February 27, 2010 ruptured the portion of the South American subduction zone separating the source regions of the 1960 and 1906 earthquakes.
A large vigorous aftershock sequence can be expected from this earthquake.
In the time period since the earthquake’s origin at 2010-02-27 06:34 to 2010-03-01 16:00 UTC, the USGS NEIC has located 121 aftershocks of magnitude 5.0 or greater. Eight of these aftershocks have magnitudes of 6.0 or greater. See Aftershock Map
Short Event-Report – Tsunami Warning – Pacific Region –
On February 27th, 2010, at 03:34 AM local time (February 27th, 2010, at
06:34 AM UTC) an earthquake occurred at the coast of Chile, near the city
Concepcion, with a magnitude Mw 8.8 in a depth of about 35 kilometres.
Because of the earthquake magnitude and the relatively shallow location of
the epicentre, there was a concrete danger of a destructive tsunami.
Therefore, the subscribers of the Tsunami Alarm System were informed of the
event shortly after the earthquake.
Tsunami reaches Japan’s Pacific side; 320,000 told to evacuate
Sunday 28th February, 06:30 PM JST
Japan observed tsunami waves as high as 1.45 meters Sunday afternoon in wide coastal areas of its Pacific side, after a massive magnitude 8.8 earthquake struck Chile on Saturday.
The Japan Meteorological Agency said it observed a 1.2-meter-high tsunami at 3:49 p.m. at Kuji port in Iwate Prefecture, while the town office of Otsuchi, also in the prefecture, reported a tsunami of about 1.45 meters at the town’s fishing port around 3:43 p.m.
Observers reported that tidal levels exceeded at one point those of piers at Kuji port and at Hanasaki port in Nemuro, Hokkaido.
The central weather agency warned that waves could still strike the coasts of the Pacific side in intervals, urging people to avoid coastal areas.
As of 6 p.m., a total of about 320,000 people in three northern prefectures—Aomori, Iwate and Miyagi prefectures—were instructed to evacuate, the Fire and Disaster Management Agency said. Residents in the city of Nemuro, Hokkaido, and in the Ogasawara islands of Tokyo were also advised to move to safer areas.
The National Police Agency said no casualties were reported as of 5 p.m.
The weather agency issued its first ‘‘major tsunami’’ warning in more than 15 years earlier Sunday following the massive earthquake that struck the central Chilean city of Concepcion.
The major tsunami warning, issued when waves of 1 to 3 meters were expected, applied to the northern Pacific coastal areas of the three prefectures, where the initial waves were believed to have occurred between 1:30 p.m. and 2 p.m. The agency last issued such a warning in July 1993 when a magnitude 7.8 quake hit Okushiri Island, Hokkaido.
In May 1960, a tsunami of between 1 meter and 4 meters struck the coasts of Hokkaido and the Sanriku region of Japan more than 22 hours after a huge M9.5 quake occurred in Chile, leaving 142 people dead or missing.
The M8.8 Chilean quake has triggered waves of 2 meters in French Polynesia and 1.5 meters in Hawaii, but no major damage from the waves has been reported.
The Japanese weather agency warned that waves of as high as 2 meters may be observed along the rest of the Pacific coast, as well as the coastal areas of the Sea of Japan in Aomori Prefecture and of Okinawa Prefecture.
In other parts of the nation, waves between 10 cm and 50 cm were observed. The agency maintained the warnings after the waves were monitored, saying bigger waves could still come.
Prime Minister Yukio Hatoyama urged people living near the shores to keep away from the sea, telling reporters, ‘‘We must not think that just because the first wave has arrived, we are safe. Tsunami is a scary thing.’‘
Yasuo Sekita, chief of the weather agency’s earthquake and tsunami observation section, said in a press conference in the morning that the agency may have to keep the warnings in place for some time because ‘‘the second and third waves could be bigger than the first.’‘
A number of local governments in the areas affected by the warnings subsequently told households along the coast to evacuate, while the Japan Coast Guard recommended ships operating near Iwate Prefecture to evacuate.
Fears of a major tsunami also affected transportation services, with East Japan Railway Co and other JR group firms halting services in coastal areas. An expressway was partly closed to traffic and some flight services have been canceled.
In the Aomori town of Oirase, the mayoral election was called off after voting started in the morning as the local election board decided to close three polling stations near the coast.
Parameter Calculation by Nagoya University
● 概略・特徴： 2月27日06時34分（UT)，チリ中部でM8.8の 地震が発生しました．震源に近いコンセプシオン（人口約２０万人）などの都市とは 連絡が未だにつかない状況の中で，すでに100名を超える方の死亡が確認されているとのこと． 高速道路が崩落したりしているようで，被害が気になるところです．津波も発生しており ，中部タルカウアノで2.3m，バルパライソとコキンボで1.3mの津波が観測されたようです．
発生時刻 震央 深さ M 10/02/27 06:34 (UT) 35.846°S 72.719°W 35 km 8.8
●データ処理： IRIS-DMCから収集した広帯域地震計記録（P波上下動44) を用いて 解析しました．
●結果： 結果を図に示します。主な震源パラメータは次の とおりです．
走向、傾斜、すべり角 = (18,20,105) 地震モーメント Mo = 1.75 x10**22 Nm (Mw = 8.8) 破壊継続時間（主破壊） T = 100s 深さ H = 32 km 最大すべり量 Dmax = 13 m
●解釈その他：ナスカプレートの沈み込みに伴うプレート境界地震です． 破壊は浅い領域に進んで行きました．そのため破壊開始点は深めですが津波が 発生したものと考えられます．
下図で ●は1990年以降に起こった地震活動（USGSによる）です． これをみるとちょうど今回の地震付近で地震活動が空白になっていることがわかります． 今回の地震の震源域付近では1939年，1830年代にも巨大な地震が起こって津波が発生している ようです． 今回の地震のすぐ南側は1960年のチリ地震(Mw9.5)の震源域です．このチリ地震では 日本にも2-3mの津波が23時間かけてやってきて，139名の方が亡くなりました． 今回も日本に津波が到達する可能性があり注意が必要です．
図１ すべり分布（コンターは1m間隔で4m以上すべったところ）．破壊開始点は ★. ●はUSGSによる地震活動．
Preliminary result of the 2010 Chile Tsunami, by Adit Gusman
Adit Gusman from Hokkaido University have done tsunami simulation generated by the 2010 Chile earthquake (Mw 8.8). The fault length and width of the earthquake are 400 x 100 km2. The fault parameters are obtained from the Global CMT solution. He used slip amount of 14 m. The initial sea surface deformation is calculated using Okada formula .
The bathymetry data used is a 5 arc-min grid system which is resampled from GEBCO 30 sec dataset. DART data from NOAA is used for comparison between the simulated and observed tsunami waveform. Tsunami model is done by solving the linear shallow water equation.
Modeling the Tsunami of 27 February 2010 in Chile
DCRC, Tohoku University
Tsunami Model Description
- Geverning Equation : Linear Shallow Water Equations
- Numerical Scheme : Leap-frog Finite Difference Method (TUNAMI-CODE of Tohoku University)
- Spatial Grid Size : 5 arc-min.
- Bathymetry Data : GEBCO
- Population Data : Landscan
Tsunami Source Model
- Mo = 2.0 x 10**22 Nm
- Fault Length / Width : 450 km / 100 km
- Source Mechanism (Strike, Dip, Slip) = (16, 14, 104) Reference :USGS
- Dislocation : 15 m
Seismic Deformation Model Result
For original resolution, click the image below.
Tsunami Model Movie(QuickTime Required)
Click to play(1.6MB)
Modeled Tsunami Height and Exposed Population
How fast can we detect the impact of natural disaster ? This is a very critical problem to be solved in order to reduce the fatalities by any kinds of natural disasters. Recent advances of seismology, numerical modeling with modern computing power, remote sensing, and GIS analysis expands the capability to detect the impact of major tsunami disaster, as reported herein.
Modeled tsunami along the Pacific coast of Japan
Modeled tsunami and exposed population in tsunami source area
- Koshimura, S., T. Oie, H. Yanagisawa, and F. Imamura, Developing fragility functions for tsunami damage estimation using numerical model and post–tsunami data from Banda Aceh, Indonesia, Coastal Engineering Journal, JSCE, Vol.51, No.3, pp.243-273, 2009
- Koshimura, S., M. Matsuoka and S. Kayaba, Integrated Approach to Assess the Impact of Tsunami Disaster, Proceedings of ICOSSAR 2009, pp.2302-2307, 2009 (Safety, Reliability and Risk of Structures, Infrastructures and Engineering Systems – Furuta, Frangopol & Shinozuka (eds.), 2010 Taylor & Francis Group, London) (Published paper)
- Dobson, J. E., E. A. Bright, P. R. Coleman, R.C. Durfee & B. A. Worley, LandScan: A Global Population Data-base for Estimating Populations at Risk,” Photogrammetric Engineering & Remote Sensing Vol. 66, No. 7, 849-857, 2000.