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earthquakes

By Sharon and Rajat

What is an Earthquake?EarthquakesEarthquakes: Vibrations (seismic waves) within

Earth materials are produced by the rapid release of energy

Earth’s crust is in constant motion because of tectonic forces

Earth’s crust can store elastic energy

When forces exceed the elastic limits and structural strength of the rocks, the rocks will break and/or move producing vibrations that travel outward in all directions

Earthquakeso The actual place underground where

the rocks break producing vibrations is called the focus focus

o The place on the surface directly above the focus is called the epicenterepicenter

What types of What types of forcesforces are created?

Compression ForceCompression Force:

force pushingpushing something togethertogether

Makes a reversereverse fault

What types of What types of forces forces are created?Tension ForceTension Force:

stretching or pulling force

Makes a normal normal fault

What types of What types of forcesforces are created?Shear ForceShear Force:

a system of forces that operates against a body from different sides

Makes a strike-slipstrike-slip fault

http://www.geo.uib.no/jordskjelv/index.php?topic=earthquakes&lang=en

http://www.geo.uib.no/jordskjelv/index.php?topic=earthquakes&lang=en

What causes Earthquakes? Movement along faults: occurs when the

energy exceeds the friction holding the sides of the fault together and is suddenly releasedreleased

.Movement of magma (volcanic)

Volcanic eruptions

Seismic WavesOriginate at the focus and travel

outward in all directions ForeshocksForeshocks: small earthquakes that

come before a major earthquake

AftershocksAftershocks: Are adjustments in the crust after in earthquake

o Smaller than main earthquake, but can cause as much or more damage. They can continue for weeksweeks to monthsmonths. Not every earthquake produces aftershocks

3 Types of seismic Waves

P wavesP waves (primary waves) Compressional wave

Particles move back and forth in the same direction as the wave

Travels the fastest

Can pass through solids and liquids (gases also)

Does not cause damage

Types of Waves

S waveS wave (secondary wave, shear wave)

Particles move at right angles to the direction of the wave

Travels slower than P waves

Can pass through solids only

Does not cause damage

Types of Waves L waveL wave (long wave, surface wave, ground

wave)

Particles move in elliptical orbit Originates on the surface after

the P and S waves go straight up from the focus and reach the surface

The L wave causes the damage and will be the strongest at the epicenter

Travels the slowest

Earthquake Safety Protect yourself from falling objects (GET UNDER SOMETHING) or stand in a hallway or doorway (watch out for a swinging door)

Do not try to go outside during the earthquake

After the earthquake and before the aftershocks, go outside

Do not return to the building until it has been inspected

Why japan is still alive after the massive earthquake

Sharon and Rajat