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Earthquakes and Seismic Waves (pages 169–175)

Earthquakes and Seismic Waves (pages 169–175). Types of Seismic Waves (pages 170–171). Key Concept: Seismic waves carry energy from an earthquake away from the focus, through Earth’s interior, and across the surface.

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Earthquakes and Seismic Waves (pages 169–175)

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  1. Earthquakes and Seismic Waves (pages 169–175)

  2. Types of Seismic Waves (pages 170–171)

  3. Key Concept: Seismic waves carry energy from an earthquake away from the focus, through Earth’s interior, and across the surface.

  4. Lesson Objective 1Students will be able to ….Describe how the energy of an earthquake travels through earth.

  5. An earthquake is the shaking that results when rocks move inside Earth. An earthquake is caused by stress along a fault. Stress increases until the rocks break and release stored energy.

  6. The place where rocks break and cause an earthquake is called the focus (FOH kus).

  7. The point on the surface directly above the focus is called the epicenter (EP uh sentur).

  8. Earthquakes cause waves, called seismic waves, to travel through Earth.

  9. Seismic waves carry the energy released by the rocks. There are three kinds of seismic waves: P waves, S waves, and surface waves.

  10. P waves move rocks back and forth, like a wave passing through a spring toy when you push in the coils. P waves are the fastest seismic waves.

  11. S waves move rocks up and down, like a wave passing through a rope when you flick it. S waves travel more slowly than P waves but do more damage.

  12. Surface waves are combined P and S waves that travel along Earth’s surface. Surface waves are the slowest seismic waves. They also do a lot of damage.

  13. Answerthefollowingquestions.

  14. When the ground shakes because rocks have moved inside Earth, it is called a(an) Earthquake

  15. S - Waves P - Waves

  16. Circle the letter of the kind of seismic waves that arethe slowest. • a. P waves • b. S waves • c. surfacewaves

  17. MeasuringEarthquakes (pages172–174) Key Concept:Three commonly used methods ofmeasuring earthquakes are the Mercalli scale,theRichter scale,and the moment magnitude scale.

  18. Lesson Objective 2 Students will be able to … Identify the scales used to measure the strength of an earthquake.

  19. The Mercalli scale is based on the amount of damage an earthquake does. For example, a weak earthquake only rattles dishes. A strong earthquake can destroy buildings.

  20. The Richter scale is based on the size of the seismic waves. A stronger earthquake makes bigger seismic waves. An instrument called a seismograph measures the size of seismic waves.

  21. The moment magnitude scale is based on the amount of energy an earthquake releases. The amount of energy is based on many things, including the size of the seismic waves.

  22. Answerthefollowingquestions.

  23. Size of seismic waves Moment magnitude scale

  24. An instrument that measures the size of seismic waves is a(an) seismograph

  25. Whichwayofmeasuringearthquakestrengthisbasedon the kind of informationshown in the drawing? Mercalli Scale

  26. LocatingtheEpicenter(pages174–175)

  27. Key Concept:Geologistsuseseismic waves tolocatean earthquake’sepicenter.

  28. Lesson Objective 3:Students will be able to ….Explain how scientists locate the epicenter of an earthquake.

  29. Theepicenteristhepointonthesurfacethatliesdirectlyabove an earthquake’sfocus.

  30. Scientists use P wavesand S waves to find an earthquake’sepicenter.

  31. PwavestravelfasterthanSwaves.SoPwavesarriveataseismographsoonerthanSwaves.PwavestravelfasterthanSwaves.SoPwavesarriveataseismographsoonerthanSwaves.

  32. ThelongerittakesS waves to reach the seismograph after P waveshavearrived, the farther away the epicenter is.

  33. To find the exact location of the epicenter,you needseismographs in three different places.You can draw a circle around each seismograph to showhowfar theepicenter is from that seismograph.The point where allthree circles cross is the epicenter.

  34. Answerthefollowingquestions.

  35. Suppose it takes a long time for S waves to reach aseismograph after P waveshavearrived.What doesthat tell you about the earthquake? a. The earthquake was strong. b. The earthquake was close to the surface. c. The earthquake wasfaraway.

  36. Is the following sentence true or false? Oneseismograph can tell youexactly where the epicenterof an earthquake is False

  37. Where is the epicenter?

  38. Nat Geo Earthquakes

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