Physics of Tsunami

By:

Febdian Rusydi

Aree Witolear

Part 1

Earthquake

Causes of Earthquake

1. Volcanic eruption

2. Meteor impacts

3. Underground explosions (like nuclear tests)

4. Movement of plates (tectonic)

Plate Tectonics

Lithosphere Comprised of many plates that slide over the lubricating athenosphere layer.

Why does it move?Fluid (magma) underneath is moving all the time.

Plate Tectonics

At the boundaries between plates1. Plates slide against each other2. Plates move apart magma

flows up to the surface3. Plates push together one

subducts the other, or neither plate subducts under the other.

San Andreas Fault

1 2 3

Earthquake at Sea1st possibility:

Earthquake at Sea2nd possibility:

Part 2

Tsunami

Tsunami

Tsunami (tsoo – nah – mee)Tsu (harbor) & nami (wave)

“A natural phenomenon consisting of a series of waves generated when water in a lake or the sea is rapidly displaced on a massive scale” (www.wikipedia.org)

Theory of Waves

Traveling Wave• Wave moves energy,

not matter!• Energy E ~ f ~ v/

T = 1/fT = 1/f

Ocean Waves

- Wind blows grab water molecules- Water’s surface stretches ripples (capillary

waves)

- Ripples moves more molecules collected- Size and momentum increase reach the

beach

Tsunami Waves

Tsunami At Sea

• Unlike a normal wave, energy of a tsunami moves through the water, not on top of it.

• Velocity:

d = water depth

Moves fast in deep waters 400 km/hour!

• No more than 1 meter high can not be seen

“…we only felt that the waves were larger than

normal.Only that!”

- Rusli, a fisherman

dgv

Energy Loss

Waves loses energy as it moves away from its source

Energy loss rate ~ 1 / wavelength

The longer the wavelength, the less energy it loses

Tsunami wavelength = 200 km!

Energy is almost constant far from epicenter

Normal Wave vs Tsunami Wave

Ocean Wave• Speed = 8-100 kph• Wave Period = 5-20

seconds apart• Wave Length = 100-

200 meters apart

Tsunami Wave• Speed = 800-1000

kph• Wave Period = 10

min-2 hours apart• Wave Length = 100-

500 km apart

As Tsunami Moves…

At the Beach

• Shallow water compresses the energy• Tsunami moving away the beach: fast, short height

v & increase, A decrease• Tsunami moving toward the beach: slow, tall height

v & decrease, A increase

Part 3

Impact

Some Pictures from Satellite

Tsunami 12/26

• Magnitude of earthquake = 9.0 SR• Slipped plate length = 1,200 km• Slip over = 15 m• Height of wave reach up to 30 m with speed ~

800 km/hr

Detected Earthquake

Tsunami Animation

Tsunami in Aceh

Magnitude: 9.0 on the Richter scale

The Energy possessed (roughly):

~ 5 MTons of TNT = 2*1018 Joules

~ 2 x explosive energy during all WW II

~ 30% energy consumed in USA a year

~ 70 days Hurricane Isabel

Impact on Earth

• Some smaller island southwest Sumatera moved ~ 20 m to southwest

• Northern tip of Sumatera moved ~ 36m to southwest

• Some small islands near Aceh province are gone forever

• New lakes/rivers created in ex-land in Aceh, disconnecting transportation to ex-villages

What we believe

• This is not a disaster, but a miracle

• Miracle that changes many things in our social life!

• The miracle is not finished yet

• We have a responsibility, to finish the miracle:

• DONATE YOUR MONEY FOR DONATE YOUR MONEY FOR ACEH!ACEH!

Poem by Heri Latief

The End

Credits: BBC, How Stuff Works