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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