1. Earthquakes

3. What are earthquakes? The word earthquake means exactly what it says. An earthquake is when the ground shakes as a result of energy being released.

4. Seismology There is an entire branch of earth science that studies earthquakes. It is called SEISMOLOGY.

5. Seismic Waves SEISMIC WAVES are waves of energy that travel through the Earth. Two types: P waves and S waves

6. Typical Seismogram http://isu.indstate.edu/jspeer/Earth&Sky/EarthCh11.ppt

7. Where do they occur? Earthquakes occur along the edges of tectonic plates The edges where they meet are called faults. A FAULT is a crack in the earth’s crust.

8. Do you see a pattern?

9. What causes earthquakes? Tectonic plates move past each other causing stress. Stress causes the rock to deform  Plastic deformation – does not cause earthquakes  Elastic deformation – rock stretches then reaches a breaking point, releasing energy.

10. What causes earthquakes? As plates push, pull, or slip past each other stress builds up. This stress causes rocks in the crust to change shape. When a rock changes shapes due to stress it is called DEFORMATION.

11. How does it happen? What happens  Real life

12. Three Types of Faults Strike-Slip Thrust (Reverse) Normal

13. Plastic Deformation Plastic Deformation- when rock changes its shape like Play-Doh® Does not lead to earthquakes

15. Elastic Deformation When rock is stretched too far, it eventually breaks.  Like a rubber band When the rock breaks it releases energy, then returns to its original shape.  It will be in a different location

16. Elastic Deformation

17. Elastic Rebound The sudden return of elastically deformed rocks to their original shape is called ELASTIC REBOUND.

18. Focus – point inside the Earth where an earthquake begins Epicenter – point on Earth’s surface above focus

19. P Waves Waves that travel through solids liquids and gasses are called P waves. “Pressure waves” Fastest and always the first waves to arrive. A.K.A. Primary waves

20. S Waves Created by rocks elastically rebounding (changing back to its original shape) Shear Waves Second fastest A.K.A. secondary waves Shear rock side to side

21. Comparing Seismic Waves

24. Locating Earthquakes http://www.uwgb.edu/dutchs/EarthSC-102VisualsIndex.HTM

25. Locating Earthquakes http://www.uwgb.edu/dutchs/EarthSC-102VisualsIndex.HTM

26. Locating Earthquakes http://www.uwgb.edu/dutchs/EarthSC-102VisualsIndex.HTM

27. We Measure Earthquakes in two ways. 1. Richter Scale 2. Mercalli Intensity Scale

28. How are Earthquakes Measured? Richter Scale

29. How are Earthquakes Measured? Mercalli Intensity Scale Click Link for Interactive Demo http://elearning.niu.edu/simulations/images/S_portfolio/Mercalli/Mercalli _Scale.swf http://elearning.niu.edu/simulations/images/S_portfolio/Mercalli/Mercalli _Scale.swf

30. Earthquake Waves & Earth’s Interior

31. Tsunamis http://www.uwgb.edu/dutchs/EarthSC-102VisualsIndex.HTM

32. Formation of a tsunami http://isu.indstate.edu/jspeer/Earth&Sky/EarthCh11.ppt

33. Tsunami Warning System http://isu.indstate.edu/jspeer/Earth&Sky/EarthCh11.ppt