1. EARTHQUAKES

2. earthquake: the shaking or vibrating of Earth caused by a release of energy

3. elastic rebound: as two plates move past each other they get stuck and then slip; the plates suddenly move, release energy and then snap back into place

4. epicenter: point on the earth’s surface directly above the focus focus: point at which rupture occurs along the fault

5. If you hear about an earthquake on the news, you will always be told the location of the epicenter. If you are told the depth of the earthquake, that is the focus.

6. fault: a break in the earth’s surface where movement has occurred

7. TYPES OF FAULTS
normal fault: blocks of rock move apart
- found at divergent boundaries

8. reverse fault: blocks move toward one another - found at convergent boundaries - also called thrust fault

9. strike slip: rocks move horizontally past one another - found at transform boundaries

10. seismology: the study of earthquakes
seismograph: device that measures earthquakes
seismogram: earthquake graph made by a seismograph

13. Seismic Waves
As energy is released from an earthquake, it is distributed in waves
Body Waves: travel through the interior of the Earth
Surface Waves: travel along Earth’s surface

14. P-wave (primary wave):
Types of Body Waves
P-wave (primary wave):
- longitudinal wave
- can travel through any material
- 1st to arrive (6-7 km/s)
- shortest period, smallest amplitude

15. S-wave (secondary wave) - transverse wave - cannot travel through liquids (outer core) - 2nd to arrive (3.5 km/s)

16. S waves cannot travel through the Earth.
P waves refract as they pass through the liquid part of the core.

17. Surface Waves - most damaging to structures - largest amplitude; slowest - last to arrive (2.5 km/s)

18. Types of Surface Waves R- Waves Rayleigh Waves
Make the ground ripple up and down

19. L-Waves
Love Waves
Make the ground ripple side to side

20. Determining the Location of the Epicenter

21. Shallow earthquakes tend to occur along transform boundaries
Shallow earthquakes tend to occur along transform boundaries. Deep earthquakes tend to occur along subduction zones. * the deeper an earthquake, the less damage it causes at the surface

22. How do we measure earthquake magnitude?

23. Richter Scale - measures amplitude of largest seismic wave 100 km from the epicenter - wave height is ten times greater for each step that increases

24. The energy released is 33 times greater for each step that is increased How many magnitude 6 earthquakes would you need to release the same amount of energy in one magnitude 8 earthquake?

25. Richter Scale values > 8 = total destruction (about 1/year)
7-7.9 = bad (18/year)
6-6.9 = moderate-serious (120/year)
5-5.9 = felt by everyone (minor damage) (800/year)
4-4.9 = not felt by everyone (6,000/year)
< 3.9 very small (about 1 million per year)

26. Moment Magnitude Scale
measures energy released
used by scientists
factors in amount of movement and rigidity of rocks

27. Comparison: 1964 Alaskan EQ Richter- 8.4, Moment – 9.2
1906 San Francisco
Richter – 8.3, Moment – 7.9

28. Mercalli Intensity Scale
measures damage done by the earthquake
- scale of I – XII

29. I – felt by few people V – felt by everyone (dishes broken) VIII – slight damage to structure X – wooden structures destroyed XII – total destruction; see waves at surface

30. Earthquakes caused by Humans
Hoover Dam –
600 tremors over the 1st 10 years; some as high as magnitude 5
Rocky Mountains –
In the 1960’s the US Army drilled a well and injected liquid waste into the mountains
This lubricated the fault and earthquakes began
When the Army stopped injecting the waste, the earthquakes stopped too

31. Earthquake Prediction
long term  years, not days or hours
short term  Good Luck!

32. In order to study earthquake predictions, you need to predict an earthquake. (in order to set up equipment, etc.)

33. - how often an earthquake of a specific magnitude occurs
Recurrence Interval
- how often an earthquake of a specific magnitude occurs

34. looking at gaps along faults where there is no seismic activity
Seismic Gap Method
looking at gaps along faults where there is no seismic activity

35. Earthquake Damage 1. Ground Displacement examples:
1906 San Fran – 7 m of displacement
1964 Alaska – 12 m of displacement (vertical)
1989 Loma Prieta 2.2 m
1994 Northridge 1 foot

36. Alaska, 1964

37. 2. Landslides
1970 Peru – killed 70,000 people

39. 3. Liquefaction
sediments act as fluids
Kobe, Japan

42. Tsunami - seismic sea wave ex. Sumatra 2004
Fire
ex. Tokyo, San Francisco

47. 1906 – San Francisco

48. 6. Valley Fever
disease
sewage lines break
- dust associated with fires causes bronchial problems

49. Most Devasting EQs 1500’s  China 850,000 dead
1923  Tokyo 143,000 dead
1976  China 250,000 dead
1985  Mexico 10,000 dead
1995  Kobe, Japan 5,000 dead
$100 billion in damages

50. Northridge 1994

51. Northridge, CA 1994

52. Northridge 1994

53. Northridge 1994

54. Alaska, 1964

55. San Francisco Bay Bridge, 1989
                                       

56. Kobe Japan, 1995