chap 12 notes earthquakes and its effects.ppt
- 1. EARTHQUAKES! EARTHQUAKES! Video: Video: Earthquakes 101 101 Chapter 12 Chapter 12
- 2. Section 1 Section 1 • Earthquakes are caused by a sudden release of energy when rocks move along a fault. • Elastic rebound is thought to cause the rocks to move.
- 3. Anatomy of an Earthquake Anatomy of an Earthquake • Focus-location of first motion in Earth • Epicenter-spot on surface above the focus The focus can be shallow or deep Shallow foci cause the most damage
- 5. Seismic Waves Seismic Waves Body Waves Body Waves: : Travel through the Earth Travel through the Earth Made up of: Made up of: - -P waves P waves: primary, fastest : primary, fastest - -S waves S waves: secondary, second fastest, travel : secondary, second fastest, travel through solids only through solids only
- 6. Earthquake Waves & Earth’s Interior Earthquake Waves & Earth’s Interior
- 7. Seismic Waves and the Earth Seismic Waves and the Earth’ ’s s Interior Interior The speed and direction of seismic waves gives The speed and direction of seismic waves gives us information about the Earth us information about the Earth’ ’s structure s structure Waves travel at different speeds through Waves travel at different speeds through different materials different materials Shadow Zones-areas where no body waves are Shadow Zones-areas where no body waves are detected detected
- 8. Comparing Seismic Waves Comparing Seismic Waves
- 9. Seismic Waves (cont) Seismic Waves (cont) Surface Waves Surface Waves Slowest moving waves Slowest moving waves May cause the greatest damage May cause the greatest damage 2 Types: 2 Types: - -Rayleigh Rayleigh -Love -Love
- 11. Earthquakes and Plate Tectonics Earthquakes and Plate Tectonics Most earthquakes occur at plate boundaries Most earthquakes occur at plate boundaries (converging and diverging) where the stress is the (converging and diverging) where the stress is the greatest greatest
- 12. How Seismographs or Seismometers How Seismographs or Seismometers Work, TB pg. 217 Work, TB pg. 217 http://www.uwgb.edu/dutchs/EarthSC-102VisualsIndex.HTM -measures ground motion and can be used to determine the distance seismic waves travel https://www.youtube.com/watch?v=Gbd1FcuLJLQ
- 13. How do scientists calculate how far a location How do scientists calculate how far a location is from the epicenter of an earthquake? is from the epicenter of an earthquake? Scientists calculate the difference Scientists calculate the difference between arrival times of the P waves between arrival times of the P waves and S waves (lag time) and S waves (lag time) The further away an earthquake is, The further away an earthquake is, the greater the time between the the greater the time between the arrival of the P waves and the S waves arrival of the P waves and the S waves They use the lag time to calculate a They use the lag time to calculate a distance to the epicenter distance to the epicenter
- 14. Typical Typical Seismogram- Seismogram- a graphical illustration a graphical illustration of EQ waves of EQ waves http://isu.indstate.edu/jspeer/Earth&Sky/EarthCh11.ppt
- 18. Section 2 Section 2 Seismographs record vibrations in the ground Seismographs record vibrations in the ground Magnitude: the strength of an earthquake, Magnitude: the strength of an earthquake, Richter scale or moment magnitude (more Richter scale or moment magnitude (more accurate) accurate) Intensity (amount of damage)-modified Mercalli Intensity (amount of damage)-modified Mercalli scale-from I-XII, oldest measurement scale scale-from I-XII, oldest measurement scale
- 19. How are Earthquakes Measured? How are Earthquakes Measured? Richter Scale Richter Scale
- 20. How are Earthquakes Measured? How are Earthquakes Measured? Mercalli Intensity Scale Mercalli Intensity Scale Click Link for Interactive Demo http://elearning.niu.edu/simulations/images/S_portfolio/Mercalli/Mercalli_Scale.swf
- 21. Predicting Earthquakes-video clip: Predicting Earthquakes-video clip: https://www.youtube.com/watch?v=gFB-qpiKccs https://www.youtube.com/watch?v=gFB-qpiKccs No reliable way to predict earthquakes: scientist No reliable way to predict earthquakes: scientist use the following information use the following information Scientists are trying to detect changes that occur Scientists are trying to detect changes that occur before an earthquake before an earthquake Seismic gaps are areas of low earthquake activity, Seismic gaps are areas of low earthquake activity, but have a history of strong activity-might be spot but have a history of strong activity-might be spot for future earthquake for future earthquake Foreshocks-small earthquakes that precede a large Foreshocks-small earthquakes that precede a large earthquake earthquake
- 22. Soil Type Soil Type Type of soil can affect how a building responds to seismic waves. Type of soil can affect how a building responds to seismic waves. NEHRP has defined six different soil and rock types based on NEHRP has defined six different soil and rock types based on their shear-wave velocity, in order to determine amplification their shear-wave velocity, in order to determine amplification effects: effects: Type A, hard rock (igneous rock). Type A, hard rock (igneous rock). Type B, rock (volcanic rock). Type B, rock (volcanic rock). Type C, very dense soil and soft rock (sandstone). Type C, very dense soil and soft rock (sandstone). Type D, stiff soil (mud). Type D, stiff soil (mud). Type E, soft soil (artificial fill). Type E, soft soil (artificial fill). *Type A having the least amplification and Type E *Type A having the least amplification and Type E the most. the most.
- 23. Section 3 Section 3 Video: Tsunamis 101 Video: Tsunamis 101 Tsunamis can form when the epicenter is on the Tsunamis can form when the epicenter is on the ocean floor ocean floor Damage to structures depends on how they are Damage to structures depends on how they are built and what type of ground they sit on built and what type of ground they sit on