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Earthquakes

This article discusses the occurrence of earthquakes, the causes behind them, and the measurement of seismic activity using the Richter scale. It also covers safety tips during an earthquake and the analysis of seismic waves by geologists.

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Earthquakes

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  1. Earthquakes

  2. Where do Earthquakes occur? • 28)Lithosphere

  3. What causes Earthquakes? • Earthquakes occur where tectonic plates are moving. • They can move towards each other, away from each other, or horizontally beside each other.

  4. #29 Geologists analyze earthquake waves (seismic waves) to determine the composition of the layers within Earth.

  5. Transform – San Andreas Fault

  6. What would you do? • 39) If you were inside a building, the best thing to do when an earthquake occurs is immediately hide under a desk or chair. • Something strong to cover your body.

  7. What would you do? • If you are outside when an earthquake begins, you should? Run away from buildings!!!!!

  8. A seismograph is a machine that measures earthquakes.

  9. A seismogram is a tracing of earthquake motion created by a seismograph.

  10. Earthquake: Epicenter & Focus Focus -The location where the earthquake begins and rocks being moving. The ground ruptures at this spot, then seismic waves radiate outward in all directions. Epicenter -The point on the Earth's surface located directly above the focus of an earthquake.

  11. Epicenter & Focus

  12. Waves and Energy Seismic Waves—A type of vibration that travels through the Earth 3 Types: • Primary (P) waves • Secondary (S) waves • Surface waves

  13. Primary (P) waves • Fastest waves!!! • Travel through solids, liquids, and gases • A type of seismic wave that compresses and expands the ground. • The first wave to arrive at an earthquake. • Least Destructive

  14. Surface waves • Move along Earth’s surface, not inside! • Travel slowest! • Most destructive

  15. Secondary (S) waves • Slower than P waves • Pass through solids only (can’t move through liquid outer core) • A type of seismic wave that moves the ground up and down or side to side

  16. Comparing P & S Waves

  17. Remember difference between waves? • P wave is the fastest wave and least destructive! • The Surface wave is the slowest wave and the most destructive. • S wave is not the fastest or slowest, it is in the middle!

  18. Shadow zone • 36)A shadow zone is formed on the opposite side of the Earth from where the earthquake occurred because S waves are blocked by liquid.

  19. Tsunami

  20. How often does an earthquake occur measuring 7.2 on the Richter scale, based on the information below?How often does an earthquake measuring 3.3 occur on the Richter scale?

  21. Why do Scientists KNOW the Earth has a liquid layer? #35 S waves are blocked by liquid. Since seismographs on the opposite side of the Earth do not receive any S waves after an earth quake so scientists have concluded that the Earth has a liquid layer

  22. Earthquake Magnitude using Richter Scale Measures earthquakes using a scale of 1-10. Moves up 1 number = an increase of almost 32 times more energy • Example: magnitude 5 earthquake = almost 32 times more energy than a magnitude 4

  23. How are Earthquakes Measured? Richter Scale

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