Giant Wave Triggered by 2004 Sumatra Earthquake

Giant Wave Triggered by 2004 Sumatra Earthquake

Page created by W. G. HuangMap credit: http://www.asiantsunamivideos.com/

Location Date UTC Magnitude Coordinates

1. Chile 1960 05 22 9.5 38.24 S 73.05 W

2. Prince William Sound, Alaska 1964 03 28 9.2 61.02 N 147.65 W

3. Andreanof Islands, Alaska 1957 03 09 9.1 51.56 N 175.39 W

4. Off the West Coast of Northern Sumatra 2004 12 26 9.0 3.30 N 95.78 E

5. Kamchatka 1952 11 04 9.0 52.76 N 160.06 E

6. Off the Coast of Ecuador 1906 01 31 8.8 1.00 N 81.50 W

7. Northern Sumatra, Indonesia 2005 03 28 8.7 2.08 N 97.01 E

8. Rat Islands, Alaska 1965 02 04 8.7 51.21 N 178.50 E

9. Assam - Tibet 1950 08 15 8.6 28.5 N 96.50 E

10. Ningxia-Gansu, China 1920 12 16 8.6 36.60 N 105.32 E

11. Kuril Islands 1963 10 13 8.5 44.90 N 149.60 E

12. Banda Sea, Indonesia 1938 02 01 8.5 5.05 S 131.62 E

13. Kamchatka 1923 02 03 8.5 54.00 N 161.0 E

Largest Earthquakes in the World Since 1900

Source: USGS Page created by W. G. Huang

Page created by W. G. HuangMap Credit: USGS

印尼蘇門答臘地震的震源參數USGS Earthquake Information Centre gives the following par

ameters for the earthquake location and magnitude.

規模 (Mw) 9.0

發震時間 (Origin time) 國際標準時間 2004/12/26 00:58:53.00

震央位置 (epicenter) 北緯 3.267 度 ; 東經 95.812 度震源深度 (Focal depth) 10 公里

Page created by W. G. HuangUSGS Earthquake Information Centre

規模 (Mw) 8.6

發震時間 (Origin time) 國際標準時間 2005/03/28 16:09:00.00

震央位置 (epicenter) 北緯 2.065 度 ; 東經 97.010 度震源深度 (Focal depth) 28 公里

2004 年 12 月 26 日

2005 年 03 月 28 日

Map Credit: EMSC Page created by W. G. Huang

Spatial and temporal aftershocks distribution from 26/12/2004 to 28/03/2005

A change in the pattern of distribution of the aftershocks is observed since January 26th. A cluster centered on Nicobar Islands appears.

Aftershocks distribution since 28/03/2005

Page created by W. G. Huang

New pattern in aftershocks distribution on April 10th ! The seismicity moved 400 km to the South-East

Map Credit: EMSC

Aftershock animation of the Sumatra earthquake of December 26, 2004

2004 年印尼蘇門答臘地震的主震與餘震分佈 (2004.12.25 ~ 2005.01.12)

Animated GIF of the seismic activity in the Sumatra- Andaman islands region from December 25, 0:00 UTC until January 12, 0:00 UTC. All epicenters shown were automatically determined using stations of the GEOFON and partner networks in the European-Mediterranean area. The time step between the frames is one hour. The color code refers to the time elapsed between the earthquake and the time indicated at the right bottom, i.e. the youngest events are always plotted in red.

Map Credit: GFZ Page created by W. G. Huang

3D Visualization of Recent Sumatra Earthquake

3D VisualizationTo view this visualization, viewers need to download and install the free viewer program iView3D

(http://www.ivs3d.com/products/iview3d).

Scripps Institution of Oceanography

The 26 December 2004 and the 28 March 2005 events are shown as red diamonds in the scene (the deeper diamond represents the 28 March event). The orange spheres represent aftershocks (magnitudes 4.7 to 6.1) in the region since 28 March 2005, and the gray spheres indicate aftershocks from the December event. The yellow spheres on the surface show the fault rupture due to the December event, and the purple cross-hairs on the surface indicate the possible error in the rupture location.

Page created by W. G. HuangCredit: University of California

U.S. Department of the Interior, U.S. Geological Survey Office of CommunicationEric Geist Released: 4/27/2005

USGS: Why the March Tsunami was Smaller than the December Tsunami


The first factor, obviously, is magnitude in March, it was 8.7, in December 9.0. the magnitude of an earthquake is a function of the rupture area and the average amount of slip throughout the rupture.

The second factor is water depth and is probably the biggest contributor to the difference in the two tsunamis, Geist said. "In December, a lot of the energy in the initial earthquake rupture occurred in deep water (about 1 to 2.5 miles), whereas the March earthquake occurred beneath the shelf just offshore mainland Sumatra at water depths of less than .6 miles or even beneath Sumatra itself.

The third factor is the depth below the surface of the earth where most of the fault slip occurred. In March, most of slip occurred at depths of 12 to 25 miles below the surface, whereas for the December earthquake, slip may have extended all the way to the sea floor at the oceanic trench.

The last factor is that there was a significant difference between the two events in the primary direction of tsunami-wave "focusing," which affects the distant or "far-field" impact of the tsunami.

2004 年 12 月 26 日印尼蘇門答臘 - 安達曼地震

Earthquake in Sumatra-Andaman on December 26th, 2005

Page created by W. G. HuangMap Credit: EMSC


Giant Thrust Earthquake & Faulting

Yuji Yagi (IISEE, BRI, 2004) Last Updated: 2005 Jan. 12

Yuji Yagi

Intitial body wave (short period) seismogram analysis shows most slip in southern 400 km (Chen Ji, Caltech)

Giant Thrust Earthquake & Faulting


Chen Ji, Caltech

Initial estimates from the aftershock distribution show the magnitude 9.0 Sumatra-Andaman Earthquake ruptured a patch of fault roughly the size of California (~ 406000 km2).

CJ's Comments:

It is noteworthy that the seismic data we used only could constrain the slip in first 220 sec. So we can not totally rule out later smaller slip occurred further north.

HENCE INITIAL REPORT:


Seth Stein and Emile A. Okal Department of Geological Sciences 1850 Campus Drive

Northwestern University, Evanston Illinois 60208 USA

Speed and size of the Sumatra earthquake Nature, 31 March 2005, vol 434 pp 581-2

Studies using body waves show that rupture started at the epicenter at the south end of this zone and propagated northward, with most of the rapid slip on the southern third of the rupture. Initial estimates (CMT solution) based on surface waves at at periods 300s and below measured a moment (4 x 1029 dyne-cm) given Mw = 9.0.

Stein and Okal indicate that Sumatra earthquake slowly released its energy by slip along a 1,200-km fault, generating a long rupture that contributed to the subsequent tsunami.


From an analysis of the Earth’s normal modes 0S2 , 0S3 and 0S4, which can be observed by Fourier analysis of long seismograms.

0S2 yields Mo = 1.3 x 1030 dyne-cm

3 times bigger than inferred from 300s surface waves (4X1029 dyne-cm) corresponding Mw is 9.3, compared to 9.0 from surface waves.

The revised estimate makes this earthquake to be the second largest earthquake (after the 1960 Chilean Earthquake, Mw=9.5) recorded since the invention of the seismometer in the late 1800s.

0S2 period 3223 s, 54 min





Comparison of predicted tsunami amplitudes assuming the entire fault ruptured or only the southern segment did.


Entire Fault

Tsunami Excitation


The largest tsunami waves would have missed Sri Lanka if only the southern segment of the fault had ruptured.

Southern Segment Only


Comparison of fault areas, moments, magnitudes, amount of slip shows this was a gigantic earthquake.

Seismic moment 2.5 times that inferred from surface waves implies slow slip on area larger

It seems that the slow slip on the northern helped to excite the large tsunami amplitudes in Sri Lanka and India.

Entire 1200-km long aftershock zone likely slipped. Consistent with split mode amplitudes and tsunami.

We now have a clearer picture of the seismic features of last year’s gigantic event

印度洋

2004/12/26 蘇門答臘地震震央

印度

馬爾地夫斯里蘭卡馬來西亞

印尼

泰國

澳大利亞

索馬利亞

馬達加斯加島

Map Credit: University of Texas Libraries

肯亞

緬甸孟加拉灣

阿拉伯海 Andaman Island安達曼群島

Nicobar Island尼可巴群島

印度洋周邊的國家分佈



TAIWAN

2004/12/26 蘇門答臘地震震央

2004/12/26 蘇門答臘地震震央與台灣的相對位置，兩地相距約3,300 公里。台灣與菲律賓因被印尼及馬來西亞擋住，沒受任何影響。


蘇門答臘島位於歐亞板塊與印度洋－澳洲板塊交界處。 2004/12/26 的強烈地震是因為印度洋－澳洲板塊潛入歐亞板塊下方，形成極不穩定的隱沒帶，蓄積的能量在一夕之間爆發，由南沿北的方向破裂，在海床上造成一道將長約1200

公里與寬約100公里的裂縫 (GFZ) 。

蘇門答臘大地震引發強烈海嘯，直撲人口稠密的南亞與東南亞諸國，受災地區猶如水鄉澤國的煉獄。根據觀測資料，這場大海嘯昨天當地時間清晨七時五十八分五十秒從位於亞齊省南南東方的震央出發，蘇門答臘濱海地區立刻被淹沒，海嘯一個小時後到達泰國西南方，兩個半小時後侵襲一千六百公里外的斯里蘭卡與印度東南岸，並繼續往六百五十公里外的馬爾地夫群島前進，餘波蕩漾一直到印度洋彼岸、非洲東部的索馬利亞才止息。

Tectonic Summary ( 地體構造 )

Page created by W. G. HuangMap Credit: U.S. Geological Survey

Page created by W. G. HuangMap Credit: Vector One GIS and Visualisation, Berlin, Germany

地體構造

Map Credit: The United Kingdom Hydrographic Office Page created by W. G. Huang

HMS Scott

Image: Royal Navy UK Page created by W. G. Huang

Images of the ocean floor near the epicentre of December's giant Asian earthquake(by the Royal Navy's hydrographic survey ship HMS Scott )

Looking south, the purple area marks where the ocean floor, which sits on the Indian tectonic plate, is pushing into, and moving under, the Burma plate. The Indonesian landmass sits atop the Burma plate. A rupture 30km below this area produced violent shaking, triggering the tsunami.

The images show clearly the boundary between the Indian and Burma tectonic plates - a region known as the Sunda Arc. The flat Indian plate shows up in purple, which turns to blue as this portion of the Earth's oceanic crust disappears underneath the Burma micro-plate (part of the Eurasian plate). The forces created by this process have rumpled and buckled the surface rocks, whose folds show up in green and yellow.

Map Credit: Compare Infobase Pvt. Ltd. 2004-05

2004 年 12 月 26 日遭受南亞地震海嘯所侵襲的地區


Here is a timeline of the disaster: 12:59 am GMT - A massive 9.0 earthquake occurs in the Indian Ocean off Sumatra, Indonesia. Huge buildings in the Thai capital of Bangkok shake under the force of the earthquake. Bangkok is nearly 2,000 km from where the earthquake took place.01:07 am GMT - After the quake, stations in Australia alert the NOAA Pacific Tsunami Warning Center of the earthquake and the potential tsunami threat.02:27 am GMT - The massive waves hit Kalmunai, Sri Lanka.

02:30 am GMT - Kattankudy is hit. By now, almost the entire east coast of Sri Lanka is under 2.7 meters of water.

02:40 am GMT - Batticaloa, Mullaitivu and Trincomalee, Sri Lanka, are hit. Yala, Thailand, is also struck by the tsunami. Though it has not yet been reported, more than 15,000 people have died. 02:57.am GMT - News wire services release the first report: "Earthquake sets off big waves." Reports of heavy damage and fatalities began to come in from Thailand's Phukit resort area. 03:00 am GMT - An AFP news correspondent in Colombo, Sri Lanka, gets a phone call from reporters in Trinco: "The sea is coming in." In the same moment, Valvettiturai and Hambantota are hit. Almost 7,000 people are washed out to sea.03:15 am GMT - A Washington Post correspondent reports a tsunami hitting Weligama, Sri Lanka. The Sri Lankan provinces of Matara, Galle and Panadura are also hit. Another 5,000 people die. 03:20 am GMT - Loaded with European tourists, the Sri Lankan resort Rae of Kalutara is hit. Satellite imagery reveals the water reaching 460 meters in from the shore line.03:30 am GMT - The AFP news correspondent in Colombo gets a call from Matara indicating that a second round of waves is coming. Waves hit the Indian coast. PTWC begins getting wire reports from the Internet about Sri Lankan casualties. Negombo, Sri Lanka, is hit. 03:46 am GMT - AFP news reports massive casualties and numbers of homeless in Sri Lanka.

04:11 am GMT - Rapidly rising water levels in India damage the coastline. Some small tremors are felt.

05:00 am GMT - PTWC advises the U.S. Pacific Command in Hawaii of the potential threat of more tsunamis in the western Indian Ocean. 05:41 am GMT - The Prime Minister of Thailand orders the evacuation of three major provinces, including Phukit.

06:09 am GMT - In a few hours, the tsunami has all but crossed the ocean, flooding Male, the capitol of Maldives.

07:15 am GMT - The PTWC advises the U.S. State Department on the continuing threat of tsunamis in Madagascar and Africa. In the next few hours, organized relief efforts begin.


(Video)

(Video) Kenya


2004 年 12 月 26 日南亞地震海嘯的影帶畫面

(Video)

(Video) Kanyakumari

(Video) Aceh

(Video) Pantong Beach

(Video)(Video)

Map Credit: Guardian Unlimited

Map Credit: Guardian Unlimited

印度16,389

A massive 9.0 earthquake Sunday off the western coast of Sumatra sent tsunami waves across the Indian Ocean, killing nearly 300,000 people.

截至 2005 年 1 月 27 日的死亡人數： 298,055

東非 137

馬爾地夫82

斯里籣卡43,832

印尼228,948

泰國8,506

馬來西亞74

緬甸59

孟加拉灣阿拉伯海

孟加拉2


Active Fault Research Center (by Kenji Satake in Tsukuba, Japan) The tsunami propagation is animated (up to 5 hours) from a 1200 km fault. The red color means that the water

surface is higher than normal, while the blue means lower. It indicates that initial tsunami to the east (e.g., Phuket) began with receding wave, while to the west (e.g., Sri Lanka) large wave suddenly reached. The darker

the color, the larger the amplitude. The tsunamis were larger in the east and west directions.

National Oceanic & Atmospheric Administration (NOAA) (download iTunes here) NOAA has run the tsunami model used to generate a world-wide picture. NOAA scientist Vasily Titov, using seismic data, rendered an animation showing how the tsunami waves propagated across the Earth. Titov used the numerical model called Method of Splitting Tsunami, or MOST. The animation covers a period of 44 hours and 27 minutes of tsunami propagation.

USGS (by Eric L. Geist) This is a local tsunami simulation using the slip distribution determine from the inversion of seismic waveforms

Institute of Geophysics and Planetary Physics at the Univ. of California (by Dr. Steven Ward) This animation shows the tsunami's progress across the Indian Ocean. It also shows some water level graphs and run-up heights throughout the region. Inundation

2004 年 12 月 26 日蘇門答臘地震海嘯之模擬動畫

Animation of Indonesia tsunami


Bureau of Meteorology, National Tidal Centre, Australia The animation covers a period of 48 hours of tsunami propagation. The tsunami reached the Atlantic and Pacific coasts of the United States about the same time.

EMSC (by H. Hebert ; LDG, Bruyeres-la-Chatel, France)

GeoForschungsZentrum(GFZ)Potsdam by Andrey Babeyko (University of Frankfurt/Main, Geophysical Institute)and Stephan Sobolev (GeoForschungsZentrum-Potsdam).

Initial sea bottom displacement is calculated following Okada’s (1985) analytical solution for the surface deformation caused by deep planar fault of arbitrary size and orientation. Tsunami wave propagation is calculated in the so-called shallow-water approximation. The model accuracy degrades in the near-shore regions.

Model zoom in Maldives (3D view animation) Model zoom in Thailand (3D view animation)

Joint Research Centre, European Commission JRC Tsunami Propagation Model

The model allows to predict the propagation wave once the initial location of the earthquake is fixed. The model, in contrast to other detailed 3d models, is extremely fast but sufficiently precise that can be integrated in the Global Disaster Alert System to give a first estimate should the conditions favour a Tsunami (magnitude > 7 and epicenter in a location under water).


左圖顯示海嘯在地震發生兩個小時後抵達普吉島與斯里蘭卡海岸，在8 到 11 小時後則到達非洲東部海岸。

2004/12/26 蘇門答臘地震海嘯在整個印度洋的走時曲線Tsunami Travel Time (in hours) for the entire Indian Ocean

主震

http://staff.aist.go.jp/kenji.satake/Sumatra.jpg Page created by W. G. Huang

the red circles indicate aftershocks occurred within 24 hours

餘震

2004 年 12 月 26 日南亞地震海嘯可侵入內陸達四公里


印尼亞齊省受到海嘯侵襲前後之衛星影像

印尼亞齊省受到海嘯侵襲後之空拍畫面

Map Credit: ABC Australia Page created by W. G. Huang

BANDA ACEH

Meluaboh Overview 海嘯前 ( 攝於 2004 年 5 月 18 日 ) 海嘯後 ( 攝於 2005 年 1 月 7 日 )

Image Credit: “DigitalGlobe” Page created by W. G. Huang

Banda Aceh Shore

海嘯前 ( 攝於 2004 年 6 月 23 日 ) 與海嘯後 ( 攝於 2004 年 12 月 28 日 ) 之衛星影像


Banda Aceh City Detail

海嘯前 ( 攝於 2004 年 6 月 23 日 ) 與海嘯後 ( 攝於 2004 年 12 月 28 日 ) 之衛星影像


Aceh, Sumatra, Indonesia

海嘯前與海嘯後之衛星影像


Banda Aceh Detail

This image was taken by Space Imaging's IKONOS satellite on Jan. 10, 2003. The image shows a portion of the northern shore of Aceh Province, Sumatra, Indonesia.

The image shows an overview of the widespread damage to structures, landmass, crops, and general infrastructure. Damage from major flooding and standing water is visible.

This image was taken by Space Imaging's IKONOS satellite on Jan. 10, 2003.

This image was taken by Space Imaging's IKONOS satellite on Dec. 29, 2004.

Images acquired and processed by CRISP, Singapore. Page created by W. G. Huang

Aceh, Sumatra, Indonesia

The image shows the western coast of Sumatra, Indonesia and Lhoknga, a village near the capital city of Banda Aceh, in the Aceh province. A white-colored mosque is in the center of the town.

The town of Lhoknga, on the west coast of Sumatra near the capital of Banda Aceh, was completely destroyed by the tsunami, with the exception of the white mosque in the city’s center.

This image was taken by Space Imaging's IKONOS satellite on Jan. 10, 2003.

This image was taken by Space Imaging's IKONOS satellite on Dec. 29, 2004.

Images acquired and processed by CRISP, Singapore. Page created by W. G. Huang

斯里蘭卡

Kalutara

海嘯侵襲前後之衛星影像


首都可倫波

Trincomalee Harbour area


SRI LANKA

Kalutara Water Detail

海嘯前 ( 攝於 2004 年 1 月 1 日 ) 與海嘯來襲 ( 攝於 2004 年 12 月 26 日 ) 之衛星影像


Kalutara Water Detail海嘯前 ( 攝於 2004 年 1 月 1 日 ) 與海嘯入侵前之退潮 ( 攝於 2004 年 12 月 26 日 ) 之衛星影像

150 公尺



普吉島

曼谷

泰國

海嘯侵襲前後之衛星影像


Similan Islands

THAILAND

The Blue Village Pakarang Resort is surrounded by a white scenic beach, natural forests and waterfalls. Only 1 hour by car from Phuket International Airport, and situated on the well-preserved Pakarang Cape, it's on one of a very few unspoiled beaches along Andaman sea in Thailand.

Khaolak, Thailand : located in Phang-Nga, a southern province on Thailand's Andaman seaboard.

海嘯前海嘯後

Page created by W. G. HuangImage Credit: “DigitalGlobe”

Sofitel Magic Lagoon Resort & Spa Khao Lak is the most luxurious choice for a tropical holiday in Khao Lak.

Khaolak, Thailand

Page created by W. G. HuangImage Credit: “DigitalGlobe”

海嘯前海嘯後

2004 蘇門達臘烈震相關新聞報導

1. CH9News (Earthquake Hits Banda Aceh)

2. BBC special news

3. CH10News (Tsunami Hits Pantong Beach and Banda Ache)

4. Tsunami Hits Patong Beach

海嘯 (Tsunami)

海嘯的英文通常被稱為 Tsunami ( 發音 : soo-NAH-mee) ，來自日語「津波」，” tsu” 指港口 (harbor) ，” nami” 指波浪 (waves) 。目前已愈來愈少人使用 tidalwave ，以便和潮汐作區別。海嘯是指海洋中綿延數百公里的波浪，在廣闊的深海大洋中其行進速度最快可高達每小時 1000 公里左右， 2004 年 12 月 26日印尼蘇門答臘地震所引發的海嘯在 75 分鐘內便前進了 600公里 (亦即時速 480 公里 / 小時 ) 。海嘯在靠近淺水區的速度則驟降，可疊加形成高度達數十公尺的水牆 (wall of water ， wave hits Patong Beach) ，這些水牆對海岸地區的衝擊往往能釀成巨大的傷亡。


Earthquake-generated tsunamis

Seafloor deformed by earthquake

Wave initiated with small amplitude and high speed in deep water

Speed decreases and amplitude increases in shallow water


Tsunami Generation:

This animation by Prof. Miho Aoki from the University of Alaska Fairbanks Art Department provides a very nice look at how a tsunami can be generated by a subduction zone earthquake.

海嘯和一般的風所引起海浪兩者有許多的不同，主要的差異在於它們的來源，速度與尺度的大小

Tsunamis and normal waves are many differences between the two. The primary differences are size, speed and source.

典型的海嘯與典型的風浪之區別Typical Tsunami Wave versus Typical Wind-generated Wave

風所引其起的波浪Wind-generated Wave

海嘯Tsunami Wave

波速 (Wave Speed)8 – 100 公里 / 小時 (kp

h)500 – 1,000 公里 / 小時 (kph)

波的週期 (Wave Period)

5 – 20 秒 (seconds)10 分鐘 (minutes) – 2 小時 (hou

rs)

波長 (Wave Length)100 – 200 公尺 (meter

s)100 – 500 公里 (km)


Major recorded tsunamisDec. 26, 2004: A 9.0-magnitude earthquake centred off the Indonesian island of Sumatra triggers tsunamis that pound the shorelines of nine countries, killing more than 226,000 people.

July 17, 1998: A tsunami triggered by a 7.1-magnitude earthquake offshore triggers a tsunami that hits Papua, New Guinea. Waves as high as 12 metres kill about 3,000 people and destroy whole villages.

June 3, 1994: Earthquakes cause a series of waves more than 60 metres high that slam into Eastern Java and Indonesia, killing 200 people.

July 12, 1993: An underwater earthquake off the coast of Hokkaido in Japan generates five-metre-high waves that leave 202 dead.

Aug. 17, 1976: Tsunamis generated by an earthquake near Mindanao, Philippines, kill 8,000.

March 27, 1964: The largest earthquake of the 20th century in the northern hemisphere, with a magnitude of 8.4., strikes off Alaska's shore. It spurs tsunami waves as high as six metres, which kill more than 120 people.

March 3, 1933: An earthquake-generated tsunami strikes Sanriku, Japan. It kills nearly 3,000 people, destroys 9,000 houses and sinks about 3,000 ships.

Nov. 18, 1929: A magnitude 7.2 earthquake occurs on the Grand Banks and is felt as far away as Ottawa. The resulting tsunami kills 28 people on Newfoundland's Burin Peninsula.

June 15, 1896: A tsunami with waves up to 30 metres high pounds the east coast of Japan around Yoshihimama, leaving about 27,000 dead.

Aug. 27, 1883: A volcanic eruption near Krakatoa, Indonesia, triggers tsunamis that kill about 36,000.


歷史上最大的海嘯 (Mega Tsunami) Lituya Bay, Alaska, on July 9, 1958 (landslide generated tsunam

i)

Map Credit: University of Texas Libraries Page created by W. G. Huang

On the night of July 9, 1958, a magnitude 8.0 earthquake occurred along the Fairweather Fault with an near Lituya Bay ( 利圖尤灣 ). The earthquake caused a large landslide in the bay, which produced a local tsunami of frightening size. The wave washed out trees to a maximum altitude of 518 meters by the time it hit the opposite slope.The volume of the rockfall was approximately 30 million of cubic meters.

歷史上殺傷力最大的海嘯East Indies on Aug. 27, 1883 (landslide generated tsunami)

The most devastating recorded tsunami demolished parts of the East Indies on Aug. 26, 1883, after the volcano Krakatau exploded. More than 36,000 people died because of the waves, which reached heights of 30 meters and speeds of 724 km/h.

Tsunami waves were recorded or observed throughout the Indian Ocean, the Pacific Ocean, the American West Coast, South America, and even as far away as the English Channel.

Total energy: 200 megatons of TNT. Hiroshima atomic bomb was only about 20 kilotonsThe amount of ejected material about 21 km3.

Child of Krakatoa


克拉卡托火山

When Krakatoa erupted in 1883, the entire northern portion of the island was blown away. On January 25,1925, a new small island was named Anak Krakatau or Child of Krakatoa that was born.

曾引起海嘯之重要歷史地震

1. 1964 年 3 月 28 日：阿拉斯加地震 (Mw = 9.2)

2. 1993 年 7 月 12 日：日本北海道地震 (Mw = 7.8)

3. 1998 年 7 月 17 日：巴布亞新幾內亞地震 (Mw = 7.1)

4. 2001 年 6 月 23 日：秘魯地震 (Mw = 8.4)


1993 年 7 月 12 日日本北海道 (Hokkaido) 地震 (Mw = 7.8)

The earthquake produced one of the largest tsunamis in Japan‘s history. At 2217 local time (1317 UTC), the quake rocked the west coast of Hokkaido and the small, offshore island of Okushiri in the Sea of Japan, generating a major tsunami. The killer waves strike with little warning. Within 2-5 minutes, extremely large waves engulfed the Okushiri coastline and the central west coast of Hokkaido, killing 202 people who were trying to flee for higher ground. Extensive damage occurred on the southern tip of Okushiri Island at the town of Aonae.

北海道

Location map of the July 12, 1993 Okushiri earthquake and tsunami. The white box outlines the source area of this event. Yellow and red circles outline the felt and damaged areas of this earthquake, respectively.


Credit : globalsecurity

The animation you will see here shows Aonae Cape, a small peninsula that points south off of Okushiri. The peninsula was completely overtopped by the giant wave, to heights of over 10 m. (the largest recorded wave runup on the island was nearly 30 m) In the image above, the wave approached from the left and swept over the land. Structures remaining after the wave attack were destroyed by the fires that engulfed the area due to broken gas lines and toppled fuel containers.

Aonae Cape,Okushiri Island

http://cwis.usc.edu/dept/tsunamis/2005/video/video_okushiri.html Page created by W. G. Huang

The tsunami generated by the July 12, 1993 Hokkaido-Nansei-Oki Mw = 7.8 earthquake produced in Japan the worst local tsunami-related death toll in fifty years [Hokkaido Tsunami Survey Group, 1993; Shuto and Matsutomi, 1995], with estimated 10-18m/sec overland flow velocities and 30m-high wave runup. These extreme values are the largest recorded in Japan this century [Hokkaido Tsunami Survey Group, 1993; Shuto and Matsutomi, 1995] and are among the highest ever documented for non-landslide generated tsunamis. We model this event to confirm the estimated overland flow velocities, and we find that current state-of-the-art shallow-water wave models can predict tsunami inundation correctly including extreme runup, current velocities and overland flow. Our results qualitatively suggest that for this event coastal inundation is more correlated with inundation velocities than with inundation heights, thereby providing one explanation why threshold-type modeling has substantially underpredicted coastal inundation in this and other recent events.

Animation (MOST Model - Method of Splitting Tsunami): 動畫 1 動畫2

Credit : U.S. National Oceanic & Atmospheric Administration (NOAA) and U.S. National Tsunami Hazard Mitigation Program

1993 Hokkaido-Nansei-Oki TsunamiVasily V. Titov

PMEL, NOAA, Seattle,Washington Costas Emmanuel Synolakis

University of Southern California, Los Angeles


Pacific Tsunami Warning CenterPTWC

Alaska Tsunami Warning Center ATWC

Hawaii

Alaska

海嘯預警系統

The PTWC was established in 1948, following the 1946 tsunami in Hawaii that left more than 150 people dead.

The ATWC was established in 1967 as a result of the 1964 9.2 earthquake in Alaska that left 132 dead—122 of those deaths have been attributed to the tsunami that was generated.

黃色表地震帶

DART station

Photo courtesy DART

Map Credit : U.S. National Oceanic & Atmospheric Administration (NOAA) and U.S. National Tsunami Hazard Mitigation Program Page created by W. G. Huang

文獻紀錄，台灣最近一次發生大海嘯、造成災害，是一八六七年的基隆，但根據中央氣象局海象預報中心觀測，台灣地區自光復以後，曾陸續發生過二、三十次小型海嘯，水位差以十幾、廿公分居多。其中以去年 (2003/12/10) ，底台東縣成功近海發生規模六．六強震後，在新港出現的七十二公分水位差小型海嘯最令人印象深刻。

氣象局海象測報中心分析台灣地區自一九一七年到一九九六年九月六日為止，發生過廿三次小型海嘯，近幾年分別在二○○二年和二○○三年各發生過一次，大多數小型海嘯水位差只有十幾、廿公分。即使有海嘯發生，最高波浪都沒有超過當日的最高潮位。一九九六年二月巴布亞紐幾內亞發生強烈地震後的三個多小時，台東縣成功就出現過小型海嘯，最高潮位上升達三十九公分。

根據海象中心觀測分析，成功和花蓮是台灣地區最常發生小型海嘯的地區，基隆近幾年也發生過小型海嘯。另一個較特別的案例是，一九九四年九月大陸福建省東山發生強烈地震時，澎湖也出現十九公分水位差的小型海嘯。至於近百年來，台灣地區發生最大規模的小型海嘯是一九八六年十一月在花蓮出現的二公尺水位差，但因是人工記錄，正確性仍有待驗證。

台灣地區的海嘯觀測


經濟部中央地質調查所新聞稿台灣會受到海嘯的威脅嗎 ?

圖一海床斷層活動引發海嘯

經濟部中央地質調查所新聞稿經濟部中央地質調查所

94 年 1 月 7 日台灣會受到海嘯的威脅嗎 ? Page created by W. G. Huang

台灣附近海域可能發生海嘯的區位及因素 ( 海底地形圖資料來源：國家海洋科學研究中心 )

根據目前地震記錄，台灣東部外海常發生大規模地震，由多數資料顯示當海底下 50 公里內的深度，發生芮氏規模 6.5 以上地震時，就有可能發生海嘯。台灣東部海岸的海底地形陡峭，近岸水深即達數千公尺，較不利於海嘯的波浪堆高，因此台灣東部未有受到海嘯侵襲造成災害的記載。但如果此次蘇門答臘大地震發生於台灣東部海域，海底地形的優勢恐怕也不能保護我們免於災難。而台灣東北部以及西南外海水深較淺，海床坡度平緩，更易受到海嘯的侵襲


94 年 1 月 7 日台灣會受到海嘯的威脅嗎 ?


圖四台灣東北海域海底斷層分佈圖

台灣東北海域為沖繩海槽最南段，由於沖繩海槽不斷的擴張，伴隨許多張裂性的斷層活動及海底火山，屬於地震活動頻繁與火山作用旺盛區域。根據目前研究指出本區域海底火山有數十幾座之多，龜山島即為其中一座露出海面的活火山，而劇烈性的張裂性斷層活動及海底火山活動都是引發海嘯的主要原因。

此外，在基隆外海的棉花嶼與釣魚台海域為沖繩海槽的北坡，海底呈現數個峽谷地形，研判這些海底峽谷可能由伴隨斷層活動的大規模的海底山崩所造成，海底山崩亦可能形成海嘯，為東部海域帶來災害。




圖五台灣東北海域海底火山分佈圖（ O 為火山的位置，△為高地熱流地點，數字 12 為龜山島）

12

台灣西南部與南部海域雖然較少活動斷層，地震頻率及規模均較本島為少，斷層活動引發海嘯的機率甚低。但是位於台灣南方的菲律賓與台灣同屬於菲律賓海板塊與歐亞板塊的聚合帶，地震頻繁，呂宋島有許多活動斷層延伸至海域，大規模斷層活動可能引發海嘯，於數十分鐘至一小時即可到達台灣西南部海域，衝擊台灣南部及西南部海岸。





下次超級海嘯，將侵襲人口稠密的美國東岸？ Discovery 在 2005 年 1 月 2 日播出《超級海嘯》節目做了這樣的預測。

《超級海嘯》節目揭露由山崩引起具恐怖毀滅力的超級海嘯，介紹海嘯成因，並大膽預測下一次超級海嘯發生的地點。科學家發現大型火山島崩塌引起的超級海嘯，將是重大的危機；科學家預測，下一次的火山島崩塌，將在北非加納利群島的拉帕馬島。

節目中的科學家假設這座島若發生崩塌，隨之產生的超級海嘯會迅速橫越大西洋，掀起的海浪會有六百五十公尺高，波長約卅到四十公里，並以七百二十公里時速向西橫渡大西洋，朝美國撲去，美東沿岸的從紐約到邁阿密均會毀於一旦。超級海嘯的肆虐範圍將深達內陸廿公里，帶來的災難規模將令人無法想像。

Page created by W. G. HuangMap Credit: University of Texas Libraries

下一波： Discovery 預測超級海嘯在美東

加納利群島 (CANARY ISLANDS)

拉帕馬島 (La Palma)

北大西洋

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