Phuket, Thailand

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Tsunamis
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Tsunamis

• Amateur videos from the 26 December 2004 tsunami
  in SE Asia
• What is a tsunami?
• What can cause a tsunami?
• Wave basics (three formulas you need to know)
• The Pacific tsnumai warning system
• How to survive a tsunami

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Aceh, Indonesia

• Shot by a wedding photographer perched on a
  rooftop in Banda Aceh, Indonesia, the tape shows
  a torrent of dark brown water flowing fast and
  furious down the street below. The water, which
  came about 15 minutes after a massive undersea
  quake rocked the area, turned the street into a
  river which carried planks, mattresses, cars,
  appliances and uprooted trees, and sent people
  scampering up the sides of buildings. The only
  sounds were those of people screaming as the
  surging torrent picked up everything in its way
  and flowed as high as the second floor of the
  buildings.

http//www.asiantsunamivideos.com/
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Phuket, Thailand

• Amateur camcorder footage of the 2004 tsunami
  disaster shot from the balcony of a motel. The
  cameraman (father) is with his wife and son
  looking towards the beach and are at first amazed
  to see a very large wave come crashing in the
  beach. A short while later a much larger wave
  suddenly appears and can be seen breaking right
  in front of the beach and has such force that
  part of it proceeds right into the resort
  instantly filling it with water and doing a lot
  of damage.

http//www.asiantsunamivideos.com/
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Phuket, Thailand

• Amateur camcorder footage of the 2004 tsunami
  disaster. Shot from inside a quickly-flooding
  restaurant in Phuket, waves engulf older couple
  clinging to railing outside before flooding
  entire room.

http//www.asiantsunamivideos.com/
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(No Transcript)
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Khao Lak, Thailand

• Shot by a Finnish tourist this footage shows the
  tsunami arriving at a beach in Khao Lak. The
  height and power of the tsunami featured in this
  video is truly amazing.

http//www.asiantsunamivideos.com/
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(No Transcript)
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Kanyakumari, India

• Amateur camcorder footage of the 2004 tsunami
  disaster. The footage captures the sudden
  crashing of a giant wave against the Vivekananda
  Rock Memorial, situated at the southern tip of
  Kanyakumari. The video was shot by Aniket Kale.
  After visiting the memorial, the 16 year-old and
  his family were waiting for a ferry to take them
  back to the mainland when the tsunami suddenly
  crashed into the memorial and the sea wall beside
  it. Hundreds of other tourists were around at the
  time. Kale and his family are from Pune in the
  western Indian state of Maharashtra.

http//www.asiantsunamivideos.com/
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(No Transcript)
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What is a Tsunami?

• Tsunami means harbor wave in Japanese.
• Previously commonly referred to as "tidal
  waves, but unrelated to tides.
• Also called "seismic sea waves" , but not always
  caused by earthquakes.

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What can cause a tsunami?

• Most common shallow earthquakes (M gt 8) that
  disrupt the seafloor
• Undersea debris flows
• Meteorite impact in the ocean

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Snapshot of a wave
Waves Basic Concepts
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Amplitude (A) The height of the wave crest above
the background surface.
Snapshot of a wave
Waves Basic Concepts
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Period (T) The time between the successive
arrivals of wave crests.
Waves Basic Concepts
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Wavespeed (V) The speed of wave propagation.
Waves Basic Concepts
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Formula 1
For all waves
V /T
Example Suppose that waves on a beach have a
wavelength of 80 m and a period of 10 s. Then V
8 m/s 29 km/h
Waves Basic Concepts
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Formula 2
For tsunamis
g d
V
where g 9.8 m/s2 is the acceleration of
gravity, and d is the water depth. Example 1 In
the open ocean, d 4000 m. Therefore V 198
m/s 713 km/h
Waves Basic Concepts
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For tsunamis
g d
V
where g 9.8 m/s2 is the acceleration of
gravity, and d is the water depth. Example 2
Near the shore, suppose that d 100 m. Then V
31 m/s 112 km/h
Waves Basic Concepts
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Formula 3
Wave amplitude formula
A2 (V1/V2) A1
Sample calculation A1 amplitude near short
10 m V1 31 m/s V2 198 m/s A2 amplitude
in open ocean 1.6 m
Waves Basic Concepts
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How do tsunamis differ from other water waves?
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Pacific Tsunami Warning System
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How to survive a tsunami

• Heed Natural Warnings
• An earthquake may serve as a warning that a
  tsunami is coming, and so may a rapid fall or
  rise in coastal waters.

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How to survive a tsunami

• Heed Official Warnings
• Play it safe, even if warnings seem ambiguous or
  you think the danger has passed.

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How to survive a tsunami

• Expect Many Waves
• The next wave may be bigger, and the tsunami may
  last for hours.

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How to survive a tsunami

• Head for High Ground and Stay There
• Move uphill or at least inland, away from the
  coast.

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How to survive a tsunami

• Climb a Tree
• As a last resort, climb up a strong tree if
  trapped on low ground.