Download - Ch. 2.1 and 2.2 Lecture PPT
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EarthquakesEarthquakes:
the shaking and trembling that results from the movement of rock beneath Earth’s surface
See simulation below:
Terashake
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Caused by STRESS
Stress: a force that acts on rock to change its shape or volume
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1. Shearing
pushes a mass of rock in two opposite directions
Causes rock to break and slip apart or to change its shape
See simulation below: http://scign.jpl.nasa.gov/learn/plate5.htm
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2. Tension
Pulls on the crust
Stretching rock so that it becomes thinner in the middle
See simulation below:
http://scign.jpl.nasa.gov/learn/plate5.htm
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3. Compression
Squeezes rocks until it folds or breaks
Compresses rock like a giant trash compacter
See simulation below:
http://scign.jpl.nasa.gov/learn/plate5.htm
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What is a Fault?A break in Earth’s crust
Slabs of crust slip past each other
Occurs along a plate boundary
Forces of plates: compress, pull, or shear the crust so it breaks
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Types of Faults Normal- caused by tension
Reverse- caused by compression
Strike-slip -caused by shearing
Fault Movements
See simulation below:
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Mountain Building From faulting
Two normal faults
From folding Anticline - forms
an arch Syncline - forms a
bowl
Plateau - large area of flat land From vertical fault
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Earthquake Terminology
Focus Point beneath
Earth’s surface where rock that is under stress breaks, triggering an earthquake
Epicenter Point on the
surface directly above the focus
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Seismic Waves P Waves First waves to
arrive
Compress and expand the ground like an accordion
Can travel through solids and liquids
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Seismic Waves S Waves Vibrate from
side to side as well as up and down
Only move through solids, not liquids
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Seismic Waves Surface waves Move slower
than P and S waves
They produce the most severe ground movements
Some roll like ocean waves
Others shake from side to side
Wave MovementsSee simulation below:
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Detecting Seismic Waves
Seismograph Records and
measures the vibrations of seismic waves
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Measuring Earthquakes Magnitude - measurement of
earthquake strength based on seismic waves and movement along faults
Mercalli Scale - rate earthquakes according to their intensity How affect people buildings, people
and land surface Richter Scale - rating of the size of
seismic waves as measured by a particular type of seismograph
Moment Magnitude Scale - estimates the total energy released by an earthquake