1. Earthquakes

2. earthquake: shaking and trembling that results from sudden movement of part of the Earth’s crust
Caused by release of energy (lithospheric plates)

3. OCCURS FOR MANY REASONS:
ground shakes from erupting volcano
collapse of a cavern
impact of meteor
major cause- stress that builds up and causes faulting

5. Elastic rebound theory: rocks that are strained past a certain point will fracture and spring back to their original shape

7. Depth inside the Earth at which an earthquake occurs depends upon the kind of plate boundary
focus: point beneath the Earth’s surface where the rocks break or move apart
Point on fault plane where 1st movement occurs

8. epicenter: point on Earth’s surface directly above the focus
site of most violent shaking
focus

9. P waves (primary): move fastest back and forth waves
3 kinds of wave motions:
P waves (primary):
move fastest
back and forth waves
move through solid, liquid or gas
push-pull waves

12. S waves (secondary): travel slower move side to side
travel through solids

15. L waves (surface):
move slowest
move like ripples on a pond

19. Examine P and S waves moving through Earth's interior.

20. Blue primary waves followed by red secondary waves move outward in concentric circles from the epicenter of an earthquake off British Columbia and Washington State.

21. Seismograph: instrument that detects and measures seismic waves

23. Seismogram:seismograph’s record of waves; has wavy lines recorded on paper

24. Seismologist: scientists who study earthquakes

25. Tracing made by a seismograph can be used to tell how far away an earthquake’s epicenter is from the station that recorded it:
Need distance from 3 different stations in order to determine location
Point where all 3 circles meet is location of epicenter

28. seismograms can be used to determine strength or magnitude of energy produced by an earthquake
Richter scale: measures how much energy an earthquake releases by assigning a number from 1 to 10- each is ~30x’s higher

30. Pacific Ring of Fire: major earthquake zone that forms a ring around the Pacific Ocean

32. Indian Ocean Earthquake
December 26, 2004

33. Examine a map showing earthquake risks.

34. Successful earthquake prediction must correctly forecast:
where it will occur
when it will occur
what magnitude it will be

35. Possible methods for prediction:
microquakes
behavior of animals
detect slight tilting of ground before an earthquake
natural gas seepage