1. Chapter 12: Earthquakes

4. Where do earthquakes tend to occur? Earthquakes can occur anywhere, but they tend to occur on and near tectonic plate boundaries.

5. San Andreas Fault, California What is a fault? A fault is a break or crack in Earth’s crust along which rocks shift their position.

6. Describing a Fault: - Fault Line - Fault Plane - Foot Wall - Hanging Wall

7. Type of Plate Boundary Type of Faulting DivergentNormal ConvergentReverse TransformStrike-Slip

8. Normal

9. Divergent

10. Reverse

11. Convergent

12. Strike-slip

13. Transform

14. Type of Plate Boundary Type of Faulting DivergentNormal ConvergentReverse TransformStrike-Slip

16. Fault Zones

17. What’s happening in CA?

18. Will CA break off and fall into the ocean?

19. Faults in Southern California

20. What is seismology? Seismology: a science that deals with earthquakes and with artificially produced vibrations of Earth

21. Seismograph: an instrument that records vibrations in the ground. Seismogram: a tracing of earthquake motion that is recorded by a seismograph.

22. ~300 miles long! shaking lasted ~1 minute felt from southern Oregon to central Nevada, and south of Los Angeles (maybe in SD?) 1906 San Francisco Earthquake M 7.7 to M7.9?

23. Massive fires followed the earthquake and burned for several days

24. Magnitude: a measure of its strength of an earthquake. Intensity: (in Earth Science) the amount of damage caused by an earthquake.

25. 1906 San Francisco Earthquake M 7.7 to M7.9? Casualties and Damage Casualties3000+ People left homeless225,000 Buildings destroyed28,000

26. 1994 Northridge, CA Earthquake M 6.7

27. 2004 Sumatra Earthquake M 9.3

28. Coastal damage from the tsunami

29. Countries most affected by the earthquake and tsunami

30. Stress and Aftershocks

31. What is happening to the Pacific plate and the North American plate? What happens along the fault?

32. At the plate boundary Elastic Rebound: the sudden return of elastically deformed rock to its undeformed shape

33. After the Earthquake

34. Near-field: Earthquake

35. What else happens after a big earthquake?

36. Aftershocks… Aftershocks are smaller earthquakes that occur after a larger earthquake – Happen near the mainshock – Are smaller magnitudes than the mainshock

38. How deep do earthquakes occur?

40. Earthquakes occur in the lithosphere

41. Earthquakes occur on faults beneath the surface of Earth

43. Focus: the location within Earth along a fault at which the first motion of an earthquake occurs

44. Epicenter: the point on Earth’s surface directly above an earthquake’s focus

47. Recording Earthquake Motion & Identifying Seismic Waves

48. Seismograph: The instrument Apparatus to measure and record vibrations Seismogram: The actual wiggle Record of an earthquake recorded by a seismograph The difference between a “Seismograph” and a “Seismogram” FuturePast

49. Waves from water drop spread out in circles

50. Earthquakes do the same thing, but in 3 dimensions

51. Seismic Waves Body Waves: in geology, a seismic wave that travels through the body of a medium. Surface Wave: in geology, a seismic wave that travels along the surface of a medium and that has a stronger effect near the surface of the medium that it has in the interior.

52. P-waves S-waves Surface waves

53. P-waves primary wave compression wave fastest of the seismic waves can travel through solids, liquids, and gases Surface waves 2 types: Love waves and Rayleigh waves Slowest seismic waves May cause the greatest damage in an earthquake S-waves secondary wave shear wave second-fastest seismic wave can only travel through solids Seismic waves

54. Surface Waves Love Waves: cause rock to move side to side and perpendicular to the direction in which the waves are traveling. Rayleigh Waves: cause the ground to move with an elliptical, rolling motion.

55. Travel time from San Diego to Los Angeles 25 seconds P-waves 25 seconds 41 seconds S-waves 41 seconds 50 seconds Surface waves 50 seconds

56. Types of Seismic Waves: P-wave, S-wave, surface wave

58. Seismic Waves and Earth’s Interior Shadow Zone: an area on Earth’s surface where no direct seismic waves from a particular earthquake can be detected. Shadow zones exist because the materials that make up Earth’s interior are not uniform in rigidity.

59. Seismic data can also be used to learn about Earth