GREEN PACKET

Earthquakes

Vocabulary

Earthquake- is a vibration in the ground that results from movement along breaks in Earth’s lithosphere.

Fault-a break in earth’s lithosphere where one block of rock moves toward, away from or past another.

Focus-where movement first occursEpicenter-the point on the surface directly above

the earthquake’s focusSeismic Waves-energy which spreads out from the

focus in all directions. (weaker the farther they are from the focus)

Vocabulary Cont.

Aftershock-is a shock that occurs after a principal shock of an EQ.

Magnitude- of an EQ is the amount of energy released by the EQ (minor=4 or less)

Seismologists-scientists who study EQs.

Faults

Normal Fault-

Reverse Fault-

Strike-Slip Fault-

P Waves-Primary Waves

Push and pull rocks causing them to vibrate in the same direction in which the wave is traveling

Travel through solids and liquids

S Wave-Secondary Wave

Cause the ground to shake side to side or up and down

Cause the rocks to move at right angles to the direction in which the wave is traveling

Slower than P waves, faster than surface waves

L Waves-Surface Waves

Most destructive at Earth’s surfaceTravel across Earth’s surface in a rolling,

wave like fashionSlowest wave

Seismograph

An instrument used to record seismic wavesUsed to determine the magnitude, or size, of

an EQThe magnitude is usually expressed using the

Richter Scale

Richter Scale

The magnitude is expressed using this scaleRepresented as a 10 fold increaseBegins at zero, but there is no upper limit to

the scale An EQ with a magnitude of 6 or higher is so

strong it can shake down buildingsUsed to report EQ activity to the general

public

Moment Magnitude

Measures the total amount of energy released by the EQ

For each increase of one unit on the scale, the EQ releases 31.5 times more energy.

Mercalli Scale

Measures the EQs intensity based on descriptions of the EQs effects on people and structures.

Scale rages from I (shaking is not noticeable) to XII (everything is destroyed)

Tsunamis

Seismic sea waves formed when an earthquake occurs on the ocean floor

Earthquakes cause the sea floor to move up and down

Most occur around the edges of the Pacific Plate

Can be predicted!

Questions

Why are EQs common in California?Are all EQs large and destructive?Where do most EQs occur?Where do strike-slip faults occur?Where do seismic waves of an EQ originate?Describe the three types of seismic waves.