1. Earthquakes An earthquake is shaking or movement of the Earth. They are caused by plate tectonics.

2. Faults Earthquakes occur on faults. Faults are fractures along blocks of rock Faults allow the blocks to move relative to one another

3. Types of Faults The direction and angle of the slip determines the type of fault. The type of fault determines the type of earthquake. During an earthquake, the rock on one side of a fault moves in relation to the other side. This is called slip. Most faults produce repeated displacement of blocks over geologic time

4. Strike-Slip Faults Strike-slip faults are nearly vertical fractures where the blocks have moved mostly horizontally. strike slip animation

5. Strike-Slip Fault Example Strike-slip faults occur in regions with transform boundaries, such as, the San Andreas Fault.

6. Bigger Faults=Bigger Earthquakes

7. More time=Bigger Earthquake

8. Normal Faults Normal faults are faults where one block has moved downward. These faults are seen in areas where there are divergent boundaries Normal Fault Animation

9. Normal Fault Examples Valley-Fairview Peaks, Nevada earthquake December 16, 1954

10. Reverse Fault Reverse faults are faults where one block moves upwards Thrust faults are reverse faults movement of 45 degrees or less Reverse Fault Animation Reverse Fault Animation

11. Reverse Fault Example Reverse faults can be found in areas with convergent boundaries. There needs to be subduction zones for reverse faults to occur.

12. Magnitude The magnitude of an earthquake is a measure of the amount of energy released by the earthquake.

13. Amount of Shaking The amount of shaking is controlled by: Magnitude  More energy released Distance  Shaking decays with distance Local soils  amplify the shaking

14. Seismic Waves When an earthquake occurs, it releases energy in the form of seismic waves.seismic waves The different types of energy waves shake the ground in different ways and also travel through the earth at different velocities.

15. Types of Waves There are two categories of waves:  Body waves travel through the Earth’s interior  Surface waves travel along or near the earth’s surface.

16. Body Waves A P wave, or compressional wave, is a seismic body wave that shakes the ground back and forth in the same direction and the opposite direction as the direction the wave is moving.

17. P Waves The fastest wave, and therefore the first to arrive at a given location, is called the P wave. The P wave, or compressional wave, alternately compresses and expands material in the same direction it is travelingP wave

18. Body Waves An S wave, or shear wave, is a seismic body wave that shakes the ground back and forth perpendicular to the direction the wave is moving.

19. S Waves The S wave is slower than the P wave and arrives next, shaking the ground up and down and back and forth perpendicular to the direction it is traveling.S wave

20. Types of Waves There are two categories of waves:  Body waves travel through the Earth’s interior  Surface waves travel along or near the earth’s surface.

21. Surface Waves: Surface waves follow the P and S waves.Surface waves A Rayleigh wave is a seismic surface wave causing the ground to shake in an elliptical motion, with no transverse, or perpendicular, motion.

22. Surface Waves A Love wave is a surface wave having a horizontal motion that is transverse (or perpendicular) to the direction the wave is traveling.

23. Magnitude

24. An estimate of the energy of an earthquake is called the Seismic Moment (M o ). Typically given in units of Newton-meters (Nm) What factors contribute to the amount of energy released by an earthquake? S = Surface Area of Fault (m 2 ) (Fault length x Fault width) D = Displacement or slip (m) µ = Rigidity of rock along the fault (N/m 2 ) Mo = S*D* µ