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Earthquake Waves

Earthquake Waves. Epicenter: point on surface above earthquake. Focus: point in Earth where energy is released. Richter Scale measures magnitude of an earthquake - a magnitude 7 has 10x more ground movement than magnitude 6. Types of Seismic Waves. Primary waves (p waves) Fastest waves

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Earthquake Waves

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  1. EarthquakeWaves

  2. Epicenter: point on surface above earthquake Focus: point in Earth where energy is released

  3. Richter Scale measures magnitude of an earthquake - a magnitude 7 has 10x more ground movement than magnitude 6

  4. Types of Seismic Waves • Primary waves (p waves) • Fastest waves • Can travel through any material • Secondary waves (s waves) • Slower than P waves • Can travel only through solids (no liquids) • Surface waves (l waves) • Energy waves that reach the Earth’s surface • Most damaging earthquake waves

  5. p-waves Speed up when going through Denser material. These are the fastest waves! Travel Through Anything primary waves push-pull waves

  6. s-waves These waves can only travel through solids. Slower than P-waves. secondary waves Travels Through Solids Only shear waves

  7. Surface waves • L – Waves • Slowest waves • Most destructive!!!

  8. Earthquake Damage & Loss of Life Depend On: • Duration of ground movement • Earthquake magnitude • Depth of focus • Type of ground particles • Building design • Fire / Landslides / Tsunami • Emergency and medical services Video on Haiti earthquake magnitude 7.0

  9. Tsunami

  10. Seismic risk in U.S.

  11. Faults in North Carolina

  12. Let’s Review…How do scientists know what the Earth’s interior is made of?

  13. By Observing Earthquake Waves

  14. Moho Boundary • Discovered in 1909 by AndrijiMohorovicic. • Boundary between Crust & Mantle. • Change in speed of seismic waves!!!

  15. Remember, Earth is composed of layers

  16. Liquid Outer Core: Iron-Nickel Liquid • S waves stop at a depth of 2900 kilometers since they cannot travel through liquids • P waves also slow down because less dense • Composed of liquid iron and nickel.

  17. Inner Core: Solid Iron-Nickel Metal • P waves speed up

  18. Seismograph – Device used to Measure Earthquake Waves

  19. Seismogram – the record of the ground shaking made by a seismograph • Determines: • Speed of Waves • Distance to earthquake’s epicenter

  20. Seismogram • Average time travel of P & S waves. • Find time between P & S wave. • Go vertically to find the distance from the epicenter.

  21. Example to Do Together:

  22. To find the Epicenter you need at least 3 stations distances! (triangulation)

  23. Locating the epicenter of an earthquake San Francisco • Use distances of earthquake from three observatories. • Use a compass • Intersection of circles determines epicenter Denver Tucson

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