1. Earthquakes
Green Packet

2. 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 occurs
Epicenter-the point on the surface directly above the earthquake’s focus
Seismic Waves-energy which spreads out from the focus in all directions. (weaker the farther they are from the focus)

3. 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.

4. Faults
Normal Fault-
Reverse Fault-
Strike-Slip Fault-

5. 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

6. 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

7. L Waves-Surface Waves Most destructive at Earth’s surface
Travel across Earth’s surface in a rolling, wave like fashion
Slowest wave

8. Seismograph An instrument used to record seismic waves
Used to determine the magnitude, or size, of an EQ
The magnitude is usually expressed using the Richter Scale

9. Richter Scale The magnitude is expressed using this scale
Represented as a 10 fold increase
Begins 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 buildings
Used to report EQ activity to the general public

10. 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.

11. 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)

12. 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!

13. 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.