1. EARTHQUAKES

2. Causes Sudden release of energy stored in rocks –Released as seismic waves Elastic Rebound Theory –Fault motion –Tectonic forces Also associated with volcanic activity

4. Seismic Waves –Focus –Epicenter –Body waves P wave –can pass through solids and fluids S wave –slower –can pass through solids only –Surface waves- most damaging Love waves Rayleigh waves

9. Locating earthquakes Seismometer –Seismograph; seismogram Determining location –Travel-time curves –Depth of focus

11. Ancient Chinese Seismometer

12. Seismic Waves

13. Travel-Time Curve

15. Measuring size of an earthquake Intensity –Modified Mercalli Scale I to XII Magnitude –Richter Scale –Moment magnitude Location & size of earthquakes in U.S.

17. Mercalli San Francisco Earthquake April 18, 1906

18. Magnitude- Richter

19. On December 18, 1737, a damaging earthquake near New York City was felt throughout most of New Jersey. The strong earthquakes off Cape Ann, Massachusetts, in 1755, the New Madrid, Missouri, area in 1811 - 1812, at Riviere-Ouelle, Canada, in 1860, Wilmington, Delaware, in 1871, New York City, New York, in 1884, and Charleston, South Carolina, in 1886, all affected New Jersey.Cape Ann, Massachusetts,the New Madrid, Missouri, area in 1811 - 1812,Charleston, South Carolina, in 1886,

20. Effects of earthquakes Ground motion Fire Landslides Liquifaction Permanent displacement of land surface Aftershocks Tsunamis- seismic sea waves

21. San Andreas Fault

31. Effects of earthquakes Ground motion Fire Landslides Liquifaction Permanent displacement of land surface Aftershocks Tsunamis- seismic sea waves

33. Tsunami Series of waves generated when a body of water, such as a lake or ocean is rapidly displaced on a massive scale.waves waterlakeoceanscale Earthquakes, landslides, volcanic eruptions and large meteorite impacts all have the potential to generate a tsunami.Earthquakeslandslidesvolcanic eruptionsmeteorite impacts potential

38. Earthquake Distribution Circum-Pacific Belt Mediterranean-Himalayan Belt Mid-oceanic ridge Benioff zones –Extend from trenches beneath continents or island arcs

43. Earthquake control Water under high pressure Release of strain

44. Earthquakes and plate tectonics Earthquakes at plate boundaries –Divergent boundaries Along sides of rift valley Indicate horizontal extension –Transform boundaries Shallow focus –Convergent boundaries Collision boundaries between continents Subduction Subduction angle

47. Earthquakes prediction Scientific techniques being explored –Microseisms –Properties of the rock –Water levels in wells –Radon emission from wells –Surface tilts & changes of elevation –Animal behavior –Patterns of earthquakes in space & time

48. This is a time-dependent map giving the probability of strong shaking at any location in California within the next 24-hours. For this purpose, “strong shaking” is defined as Modified Mercalli Intensity (MMI) VI, or the level of shaking that throws objects off shelves.

49. The Earth’s Interior Most of what we know is from geophysics

50. Evidence from Seismic Waves Seismic Reflection Seismic Refraction

54. Earth’s Internal Structure The Core –P-wave Shadow Zone – S-wave Shadow Zones –Liquid Outer Core –Solid Inner Core

56. S-Wave Shadow Zone

57. Earth’s Internal Structure The Earth’s Crust –Continental crust- sial Less dense and thicker than oceanic crust –Oceanic crust- sima –Mohorovicic discontinuity

58. P-Wave Velocities & Boundaries Moho

59. Earth’s Internal Structure The Mantle –Ultramafic Rock –Lithosphere Crust & uppermost mantle –Asthenosphere Low velocity zone –Lower mantle

61. Earth’s Internal Structure Composition of the Core –Made of metal The Core-Mantle Boundary –Convection in both core and mantle