EarthquakesEarthquakes:

the shaking and trembling that results from the movement of rock beneath Earth’s surface

See simulation below:

Terashake

Caused by STRESS

Stress: a force that acts on rock to change its shape or volume

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

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

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

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

Types of Faults Normal- caused by tension

Reverse- caused by compression

Strike-slip -caused by shearing

Fault Movements

See simulation below:

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

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

Seismic Waves P Waves First waves to

arrive

Compress and expand the ground like an accordion

Can travel through solids and liquids

Seismic Waves S Waves Vibrate from

side to side as well as up and down

Only move through solids, not liquids

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:

Detecting Seismic Waves

Seismograph Records and

measures the vibrations of seismic waves

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