1. Earthquakes & Earth’s Interior Chapter 8 pg 217

2. Bill Nye on Earthquakes  http://www.youtube.com/watch?v=RwDEysDCsoM http://www.youtube.com/watch?v=RwDEysDCsoM

3. A. What is an Earthquake? 1. Earthquakes a. A vibration of Earth produced by rapid release of energy within the lithosphere b. Happen along a fault c. Fault – fracture in the crust where movement occurs

4. d. Focus 1) Place where earthquake starts 2) Along a fault beneath surface 3) Energy goes out in all directions 4) Energy travels as seismic waves

5. e. Epicenter – place on surface directly above focus

6. f. Faults and change to earth’s surface 1) Vertical movement a) Known as uplifting b) Fault scarp – sharp edge ridge 2) Horizontal - displacement

8. Imperial fault - displacement

9. 2. Cause of Earthquakes (Elastic rebound hypothesis) a. Convection currents move plates on both sides of fault b. Rocks bend and store elastic energy c. Resistance from friction is overcome d. Rocks slip at weakest point (fault)

10. e. Causes forces farther up fault resulting in more slippage f. Continues until energy is released and rock returns to previous state

11. Elastic Rebound Page 220 figure 4

12. g. Aftershocks 1) Smaller than original quake 2) Happen after original quake 3) Caused from additional movements along the fault 4) Cause damage to previously weakened buildings

13. Effects of initial earthquake

14. h. Foreshocks – small quakes before large earthquake i. Fault segments behave differently 1) Fault creep – slow gradual movements 2) Regular slippage 3) Stay locked for extended periods of time

16. B. Measuring Earthquakes 1. Intro a. Seismology – study of earthquake waves b. Seismographs – record earthquake waves c. Seismogram – recorded ground motion

18. Seismographs ThenNow

19. 2. Earthquake waves a. Spread out in all directions b. Surface waves 1) Travel along earth’s outer layer 2) Up/down & side/side motion 3) Most destructive waves

20. 4) Change volume of material temporarily by pushing/pulling 5) Slowest waves 6) Recorded by seismogram

21. c. Body waves 1) Travel through earth’s interior 2) P waves a) Push-pull waves (compress/expand) b) Push/pull rocks in direction wave travels c) Known as compression waves d) Fastest waves

23. 3) S waves a) Shake particles at right angles to their direction of travel b) Transverse waves c) Change shape of material they pass through temporarily d) Gases and liquids will not transmit them b/c there is no elastic rebound to original shape

26. 3. Locating an Earthquake a. Earthquake distance 1) Find time b/w 1 st P wave and 1 st S wave 2) Use a travel-time graph

27. b. Earthquake Direction 1) Need 3 seismic stations 2) Circles are distance of epicenter 3) Intersecting circles shows epicenter

29. c. Earthquake zones 1) Circum-Pacific belt a) Ring of fire b) Outer edge of Pacific Ocean c) 75% of world’s earthquake activity d) Philippines, Japan, Chile, Alaska 2) Mediterranean-Asian belt 3) Oceanic ridge system

30. 4. Measuring Earthquakes a. Intensity – measures shaking based on amount of damage b. Magnitude – measures seismic waves c. Richter Scale 1) Based on amplitude of largest seismic wave 2) Logarithmic scale

31. Richter Scale and Magnitude

32. 3) Only useful within 310 miles of epicenter 4) Scientists no longer use it, but the news does

33. d. Moment Magnitude 1) More accurate than Richter scale 2) Based on amount of displacement along fault 3) Only scale that estimates energy released by earthquakes

34. 4) Calculating: a) Average amount of movement along fault b) Area of surface break c) Strength of broken rock

35. C. Destruction from Earthquakes Why does one building have almost no damage to it?

36. 1. Factors a. Intensity b. Duration c. Material used in buildings d. Building design

37. 1) Wood and steel frames = more flexible 2) Concrete needs to be reinforced

38. e. Liquefaction 1) Happens to loosely packed saturated soils 2) Soil turns into a liquid 3) Buildings settle, underground structures rise http://www.youtube.com/watch?v=4Uwxr42JqYQ

39. 2. Tsunamis a. Causes 1) Ocean floor is displaced vertically 2) Underwater landslide

40. b. Characteristics 1) Move quickly in open ocean 2) Can go unnoticed 3) Waves slow and increase in size as depth decreases

41. c. Warning system 1) Use water levels in tidal gauges 2) Provides about 1 hour warning Importance http://www.youtube.com/watch?v=noq8FYvRqgs

42. 3. Other dangers a. Landslides 1) Most damage 2) Landslides, slopes fail, ground collapses, gas and water lines break b. Fire

43. 4. Predicting Earthquakes a. Short-range 1) Study uplift, strain in rocks, water levels, pressure in wells, radon gas emission, electromagnetic properties in rocks 2) Hasn’t been successful

44. b. Long-range 1) Probability of certain magnitude earthquakes happening w/in 30-100+ yrs 2) Important for building codes 3) Based on that earthquakes are cyclical 4) Study seismic gap – no activity for long periods of time 5) Limited success

45. D. Earth’s Layered Structure 1. Intro a. We have only drilled 7.5 miles b. How do we know what the inside looks like? - Studying earthquake waves

46. c. Waves speed up with depth b/c of pressure d. Pressure causes waves to refract

47. 2. Layers by composition a. Crust 1) Oceanic a) 7 km (4mi) b) Igneous rocks (basalt) c) Younger than continentalrocks d) Ave. density 3.0 g/cm 3

48. 2) Continental a) 8 – 75 km (5-47mi) b) Average 40 km c) Older than oceanic crust

50. b. Mantle 1) Middle layer 2) 1795 miles 3) Density 3.4g/cm3 c. Core 1) Iron-nickel alloy 2) Density 13 g/cm3 3) 2162 miles

51. 3. Layers by physical properties 1) Lithosphere a) Rigid shell b) Crust and upper mantle 2) Asthenosphere a) Upper mantle b) Rocks near melting point c) Putty like substance

53. 3) Lower mantle a) More rigid but still can flow b) Bottom part is much more fluid from heat from core 4) Outer core a) Liquid b) Flowing causes magnetic field 5) Inner core – solid from pressure

55. 4. Discovering layers a. Finding crust/mantle 1) Moho discontinuity – place where seismic waves speed up 2) Named after Andrija Mohorovicic

57. b. Finding outer core (fig 16 pg 236) 1) P waves bend around liquid core 2) Shadow zone – p waves arrive minutes slower than expected through outer core 3) S waves can’t go through liquid

60. S waves don’t go through core

61. E. Earthquake Safety 1. Before a. Go over safety until it is instinctive b. Teach everyone c. Have emergency supplies 1) Battery radio 2) Batteries 3) First aid kit 4) Water and food for 2 weeks 5) Blankets

62. d. Arrange home for safety 1) Heavy things on bottom shelf 2) Breakables with latched doors 3) Don’t hang heavy things (mirrors, pictures, etc.) above where people sleep 4) Anchor heavy appliances 5) Flammable liquids away from ignition sources (water heaters, stoves, furnaces)

63. e. Locate main turn-offs (water, gas, and electric) 2. During a. Stay inside b. Move: 1) Under desk or table 2) Interior wall 3) NOT by windows, mirrors, fireplaces, and hanging objects

64. c. If cooking – turn off stove and take cover d. If outside 1) Move to open area 2) Get away from buildings, power lines, and trees

65. e. If driving 1) Stop on side of road 2) Don’t stop under bridges and overpasses, power lines, trees, large signs 3) Stay in car

66. 3. After a. Check for injuries b. Check for damage to see if you are safe c. Smell gas – open windows and get outside d. Smell/see frayed wires – turn off electric and get outside

67. The New Madrid Fault  https://www.youtube.com/watch?v=7kc7pJ8f1aY https://www.youtube.com/watch?v=7kc7pJ8f1aY