1. Earthquakes
I-880, Oakland, CA (October 1989)

3. Magnitude 5+ earthquakes 1980 - 1990

4. Earthquake Formation
Earthquakes occur when rock’s under stress shift along a fault.

5. Elastic rebound theory states that rocks under stress will strain and then “rebound” back after plates slide past each other. (this causes earthquake and possibly tsunami’s)

8. Earthquake focus and epicenter
Focus: area where fault slip occurred.
Epicenter: point on earth’s surface above focus.

9. Finish Earth’s Deadliest Earthquakes

10. Earthquake Basics What is an Earthquake? Causes of Earthquakes
Elastic Rebound Theory
How are earthquakes measured?
Seismometers/Seismographs

11. Types of Earthquake Waves
P (primary) waves
Compressional (push-pull)
Fastest waves (first to arrive at seismograph)
Move through all materials

12. Evidence of P-wave motion

13. Types of Earthquake Waves
S (secondary) waves
Move perpendicular to P wave
Second fastest waves (next to arrive at seismograph)
Move ONLY through solids

14. Types of Earthquake Waves
Surface waves
Rolling motion
Slowest waves (arrive last at seismograph)
Cause most damage

15. Seismometer

16. A seismogram records wave amplitude vs. time

18. Locating an Epicenter
View Seismograms
Measure P and S wave arrivals

19. P S

20. Locating an Epicenter View Seismograms Measure P and S wave arrivals
Measure S-wave “lag” time ( = S - P)
Use Travel-Time graph to correlate distance.

21. Locating an Epicenter View Seismograms Measure P and S wave arrivals
Measure S-wave “lag” time ( = S - P)
Use Travel-Time graph to correlate distance.
Triangulate Distances

23. PRACTICE TIME!!

26. Seismogram

33. Shadow Zone P-waves reflect between 0-104
P-waves refract between
S-waves only reflect
Proves outer core is LIQUID!

35. Measuring Strength Earthquake Magnitude
Charles Richter designed first scale
Based on height of the largest seismic wave
Every 1 increase in magnitude = 10x increase in strength

36. Earthquake Damage: Liquifaction

37. Earthquake Damage: Liquifaction

38. Earthquake Damage: Liquifaction

39. Tsunami Formation

40. Tsunami travel time (hours; simulation)
NOAA

41. Dec Sumatra Tsunami

42. Current Seismic Events
Earthquakes
Tsunami

43. References Used http://science.howstuffworks.com/earthquake6.htm