Tsunamis. Amateur videos from the 26 December 2004 tsunami in SE Asia What is a tsunami? What can...

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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

Aceh, IndonesiaShot 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/

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.

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.

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.

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.

• 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.

What is a Tsunami?

• Most common: shallow earthquakes (M > 8) that disrupt the seafloor

• Undersea debris flows

• Meteorite impact in the ocean

What can cause a tsunami?

Wavelength ( ): The distance between successive wave crests (peaks).

Wavelength can also be calculated by doubling the distance between a crest and a trough.

Snapshot of a wave

Waves: Basic Concepts

Amplitude (A): The height of the wave crest above the background surface.

Snapshot of a wave

Period (T): The time between the successive arrivals of wave crests.

Wavespeed (V): The speed of wave propagation.

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

Formula 1

For tsunamis:

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

Formula 2

For tsunamis:

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

Wave amplitude formula:

Sample calculation:

A1 = amplitude near short = 10 m

V1 = 31 m/s V2 = 198 m/s

A2 = amplitude in open ocean ~ 1.6 m

A2 = (V1/V2) * A1

Formula 3

How do tsunamis differ from other water waves?

Pacific Tsunami Warning System

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.

– Heed Official Warnings • Play it safe, even if warnings seem ambiguous or

you think the danger has passed.

– Expect Many Waves • The next wave may be bigger, and the tsunami

may last for hours.

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

coast.

– Climb a Tree • As a last resort, climb up a strong tree if trapped

on low ground.

Tsunamis. Amateur videos from the 26 December 2004 tsunami in SE Asia What is a tsunami? What can...

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