Lecture 16 - Tsunami Case Studies and Mitigation Flashcards
What was the deadliest tsunami of all time?
the 2004 Indian Ocean tsunami
What was the 2004 Indian Ocean tsunami caused by?
It was caused by a Mw 9.2 earthquake — the third largest ever recorded — on the Sunda megathrust fault, where Indo-Australian oceanic lithosphere subducts beneath Sumatra, Indonesia.
What was the rupture duration, length and peak slip of the earthquake that caused the 2004 Indian Ocean tsunami?
The ∼8-minute-long earthquake broke a fault length of ∼1,300 km (the longest rupture duration and length ever observed) with peak slip of ∼20 m.
How many people did the 2004 Indian Ocean tsunami and earthquake kill in Indonesia?
The earthquake and tsunami killed ∼160,000 people in Indonesia.
How high were run ups in Indonesia during the 2004 Indian Ocean tsunami?
> 30 m
Why were so many people killed by the 2004 Indian Ocean tsunami?
There was no warning system in place for the Indian Ocean.
How many people were killed by the 2004 Indian Ocean tsunami? (not including Indonesia)
∼60,000 in thirteen other countries across the Indian Ocean, as far away as South Africa.
How long did the 2004 Indian Ocean tsunami take to reach Sri Lanka, India, and Thailand?
two hours after the earthquake
How high were run ups in some areas of Sri Lanka, India, and Thailand during the 2004 Indian Ocean tsunami?
> 10 m
What was the 2011 Tohoku (Japan) tsunami caused by?
It was generated by a Mw 9.0 megathrust earthquake (the fourth largest ever recorded) along the Japan trench, where the Pacific plate subducts westwards between the island of Honshu.
How was the 2011 Tohoku (Japan) tsunami different from the 2004 Indian Ocean tsunami?
The Japanese authorities issued a major tsunami alert immediately after the earthquake.
Why did the sheer size of the wave in the 2011 Tohoku (Japan) tsunami take people by surprise?
The Japan trench had hosted several Mw 7–8 earthquakes in the previous century, but it was thought that a Mw 9 earthquake was impossible.
How did tsunami defences hold up in the 2011 Tohoku (Japan) tsunami?
The wave overtopped tsunami walls that were the tallest in the world and flooded areas that were assumed safe.
What was the maximum run up height in the 2011 Tohoku (Japan) tsunami?
Maximum run-up heights were ∼40 m (at Miyako).
What was the maximum run up distance in the 2011 Tohoku (Japan) tsunami?
Maximum run-up distances were ∼8 km (at Sendai).
How many people died in the 2011 Tohoku (Japan) earthquake and tsunami?
Around 18,500 people died in the earthquake and tsunami, ∼93% by drowning.
Waht were the economic costs associated with the 2011 Tohoku (Japan) earthquake and tsunami?
The economic costs exceeded US $3.6 billion, making this the costliest natural disaster ever.
Why did only a few fatalities occur outside Japan asa a result of the 2011 Tohoku tsunami?
Due to a successful Pacific- wide alert.
What was the 1958 Lituya Bay tsunami caused by?
A Mw 7.8 earthquake triggered a huge rockfall at the head of Lituya Bay, an uninhabited inlet in southeastern Alaska. A ∼30,000,000 m³, intact slab of rock plunged directly into deep water at the head of the bay, causing a giant wave to run up the hillside opposite.
Up to what height were trees stripped away by the 1958 Lituya Bay tsunami?
Up to a height of ∼500 m above sea-level, a peak run-up that ranks this the largest amplitude wave in modern history.
Why is the 1958 Lituya Bay tsunami considered a local tsunami?
The effects of the tsunami were hardly visible outside of the narrow inlet, making this an example of a local tsunami.
How many people were killed by the 1958 Lituya Bay tsunami?
Three fishing boats had anchored near the entrance to the fjord; two were sunk, drowning two people (two others survived), while the third boat, remarkably, rode out the ∼25 m high wave and was left undamaged.
What is another example of a tsunami caused by a rock fall?
The June 2017 Nuugaatsiaq tsunami (which killed four people in a small community in western Greenland) was also generated by a large rockfall on steep hillslopes above a fjord, though in this case there does not appear to have been an earthquake trigger.
What was the trigger for the 1929 Grand Banks tsunami? (Newfoundland/Nova Scotia, Canada)
A Mw 7.2 intraplate strike-slip earthquake which then triggered collapse of the steep continental slope in a huge submarine landslide.
