(4b) Tsunamis

Introduction to Geophysics and Planetary Physics

Geophysics 80

Tsunamis

The Japanese word Tsunami means „harbor wave“ (above, wood carving by Hokusai – note Fuji San in the back). Far right: Simulation of the Tsunami, caused by the 1960 Chile earthquake, which lead to sever devastation in Hawaii (right) and in Japan (Source: USGS).

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Tsunamis

A Tsunami caused by a submarine earthquake (schematic). In contract to normal ocean waves the whole water column is in motion. Right: Tuna fish, left in Maumere on the Island of Flores (Indonesia) after the 1992 tsunami (Source: P&S, 1994).

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Lisbon, 1755

The Great Lisbon Earthquake was one of the most important natural disasters. On November 1, 1755 the west coasts of Portugal, Spain and Morocco were hit by a tsunami. The five to ten meter wave killed 60 000 people in Lisbon alone. It was – until December 2004 – the most severe Tsunami in (human) history. Pictures: http://nisee.berkeley.edu/elibrary/browse/kozak.

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Krakatoa, 1883

In 1883 Krakatoa erupted after 200 years of silence (left, G. Symmons). The tremendous explosion could be heard as far as 4000 km. It caused a Tsunami, which was responsible for most of the 36 000 casualties. The paddle steamer “Berouw” was moved several kilometers inland. Anak Krakatau „The child of Krakatoa“ (above, NASA) rises continuously.

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Lituya Bay, 1958

Lituya Bay is a fjord located in southern Alaska (http://www.usc.edu/dept/tsunamis).

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Lituya Bay, 1958

On July 9, 1958 the Lituya Bay was overrun by the largest impulse wave ever recorded, caused by an earthquake (M=7.9), that trig-gered an enormous landslide. 30 Million m3 of rock fell into the sea and imitated a 520 m wave. On the other side of the bay the forest was completely erased up to a height of about 400 m.

Source: UoSC

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A Latent Risk

Debris fans on the ocean floor around the Hawaiian islands are the remnants of giant landslides in the past (left). These events caused tsunamis with wave heights way above 100 m. This also explains the (up to then) enigmatic discovery of large coral blocks on the island of Lanai – 325 m above sea level. Source: “Spektrum der Wissenschaft, 6/2004”.

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Only the satellite “Quickbird” saw the reflux of the first tsunami wave near the city of Kalutara on the west coast of Sri Lanka at 10:20 local time (far left). In the following wave trough the water retreated up to 300 Meter from the shore (left). All pictures: „Spektrum der Wissenschaft 2/2005“.

cm

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Indian Ocean, 26. 12. 2004

Satellite measurements of the wave height on the open ocean (Source: NOAA).

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Indian Ocean, 26. 12. 2004

Aceh, Sumatra (Source: DLR)

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Indian Ocean, 26. 12. 2004

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Indian Ocean, 26. 12. 2004

Aceh, Sumatra (Source: DLR)

Indian Ocean, 26. 12. 2004

Source: National Institute of Advanced Industrial Science and Technology, Japan

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Japan, 11. 3. 2011

Even more devastating than the strong earthquake itself was the tsunami that reached the east coast of Honshu only a few minutes later – with waves up to 20 m (Source: Kyodo)

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Japan, 11. 3. 2011

Containers (above, picture: Itsuo Inouye) and ships (top left: NHK, bottom left: Kyodo) were thrown around like toys.

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Japan, 11. 3. 2011

Source: Kyodo

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Japan, 11. 3. 2011

The wave moved inland as far as 5 km. Satellite pictures before (left) and after the tsunami (right) show the dimension of devastation, as near the city of Natori (Source: GeoEye)

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Japan, 11. 3. 2011

The coast near Kashima (Pictures: Digital Globe)

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Japan, 11. 3. 2011

Entire cities, like Riku Zentakata became completely erased (Source: Kyodo)

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Tsunamis und Gravity Waves

The Tsunami waves initiated atmospheric gravity waves, which affected (due to density-fluctuations in the thermosphere caused) even the orbit of the satellite GOCE (Source: ESA)

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Tsunami, Gravity Waves, and TIDs

The gravity waves, intitiated by the Tsunami, could even be observed in the ionosphere, where they caused Travelling Ionospheric Disturbances (TIDs) (Credit: NASA)

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Protective Barriers

Also in southern Japan they assessment of possible tsunami wave heights changed dramatically (Credit: Nature).

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Purple circles: Earthquakes with M > 7.5. The earthquake in Crete in the year 365 AD caused a tsunami, which killed up to 50 000 People in Alexandria. The Messina earthquake 1908 had a death toll of 70 000. The thereby released tsunami killed more than 1000 (Spektrum d. Wiss.).

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Tsunamis in Europe

Tsunamis in Europe

About 8000 years ago, a giant landslide occurred on Mt. Etna: 25 km3 of rocks and debris dumped into the Ionian Sea, thereby causing a tsunami, which could be traced as far as Israel. The simulation also (nicely) shows the effect of interference (Source: Pareschi et al., GRL, 2006).

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