Earthquakes(1)

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  • 1. EARTHQUAKE
  • 2. Earthquakes
  • 3. Types of earthquake Tectonic earthquakes these occur when rocks in the earth’s crust break due to geological forces created by the movement of tectonic plates. Volcanic earthquakes occur in conjunction with volcanic activity.
  • 4. Collapse earthquakes are small earthquakes in underground caverns and mines. Explosion earthquakes result from the explosion of nuclear and chemical devices.
  • 5. Focus and Epicenter • FOCUS = place deep within the Earth and along the fault where rupture occurs • EPICENTER = geographic point on surface directly above focus
  • 6. Seismologists are scientists that study earthquakes and seismic waves. Seismic Waves – shock waves of energy sent out as the crust shakes Seismograph is the instrument they use to obtain a record of seismic waves from all over the world.
  • 7. Seismograms zigzag line made by a seismograph. • Amplitude of seismic waves (how much rock moves or vibrates) • Distance to the epicenter • Earthquake direction
  • 8. Types of seismic waves 1. Body waves -- travel through interior 2. Surface waves -- travel on surface of earth Slowest
  • 9. 2 kinds of Body Waves 1.P-waves (Primary waves) Fastest of the three waves and the first detected by seismographs. • Can travel through Earth’s interior in less than an hour • Pass through solids & liquids • As they pass through the liquid of the outer core they change directions • As they return to Earth’s surface they cause back-and-forth motions of rock
  • 10. 2. S-waves (Secondary waves) • Travel slightly slower than P waves • When they reach Earth’s surface they cause it to move up and down • They can travel ONLY through solids • When they pass through the mantle to the liquid core they lose their energy and do not return to the surface
  • 11. 2 types of Surface waves 1.Love waves– that move like S waves but only horizontally. 2.Rayleigh waves– that move both horizontally and vertically in a vertical plane pointed in the direction of travel
  • 12. EARTHQUAKE WAVES P waves move through solids & liquids S waves move through solids only!!!
  • 13. EARTHQUAKE DAMAGE • Landsides • Building damage • Liquefaction
  • 14. LIQUEFACTION • Results in a loss of soil strength & the ability of the soil to support weight when a solid (sand and soil) becomes saturated with water and acts like a heavy liquid
  • 15. EARTHQUAKE DAMAGE Most caused by SURFACE waves (arrive last)
  • 16. • Foreshocks are small bursts of shaking that may precede a large earthquake. • Aftershocks are small tremors that follow an earthquake, lasting for hours or even days after the earthquake.
  • 17. EARTHQUAKE INTENSITY Modified Mercalli scale= measurement of damage to structures • From I to XII (Roman numerals) • Descriptive, changes with distance from epicenter • Can change from location to location What you need: • Your senses! measures damage to man-made structures at certain location
  • 18. EARTHQUAKE WAVES P waves move through solids & liquids S waves move through solids only!!!
  • 19. EARTHQUAKE WAVES Lets test your understanding!! Is this a P or an S wave? P wave! S Wave
  • 20. EARTHQUAKE INTENSITY Modified Mercalli scale= measurement of damage to structures • From I to XII (Roman numerals) • Descriptive, changes with distance from epicenter • Can change from location to location What you need: • Your senses! measures damage to man-made structures at certain location
  • 21. EARTHQUAKE MAGNITUDE measures the size of seismic waves  the energy released by the earthquake Richter scale=measurement of energy released based upon wave amplitude (size of vibration) • <2 to ~10 • Amplitude of wave goes up by 10 (Logarithmic scale)
  • 22. VOLCANOES
  • 23. VOLCANOES • An opening in Earth’s surface through which melted rock, hot gases, rock fragments, and ash burst forth, or erupt • Volcano – comes from the ancient Roman god of fire, Vulcan • Start 37 – 100 miles below surface • Rock melts and is called Magma