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Earth Systems 3209

Earth Systems 3209. Reference: Chapters 4, 15, 16, 19; Appendix A & B. Unit: 4 The Forces Within Earth. Unit 4: Topic 4.3. Properties of Seismic Waves. Focus on . . . identify the different seismic waves and describe the properties of each. Primary Wave. Secondary Wave.

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Earth Systems 3209

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  1. Earth Systems 3209 Reference: Chapters 4, 15, 16, 19; Appendix A & B Unit: 4The Forces Within Earth

  2. Unit 4: Topic 4.3 Properties of Seismic Waves Focus on . . . • identify the different seismic waves and describe the properties of each.

  3. Primary Wave Secondary Wave Rayleigh Wave Love Wave Seismic Waves • The source of anearthquake is called the focus and the epicenter is the point onEarth’s surface directly abovethe focus. • Seismicwaves originate at the focus and travel outward in all directions. • These energy waves are classified as; 1) Body Waves: 2) Surface Waves: Text Reference Pages 445 - 447

  4. Originate from the focus and travel inall directions through thebody (Interior) of the Earth. These waves can pass through solids, liquids, and gases. P-waves move by compressing and expanding (push-pull motion) the material as it travels. Much like sound waves. 1) Primary Wave (P-Wave) These waves have the greatest velocity (6 km/sec) and are the first to reach the seismograph stations. Vibrate in the same direction aswave motion. Rarefaction Vibration Direction Compression Seismic Waves – Body Waves

  5. Originate from the focus and travel inall directions through thebody (Interior) of the Earth. S-waves travel through material by shearing it and vibrate in adirection perpendicular to the wave motion. These waves are much like the waves on the ocean. Because liquids and gases have no shape, these waves do not pass through liquids or gases, only trough solids. 2) Secondary Wave (S-Wave) These waves travel through Earth slower (3.5 km/sec.) and are the second to reach seismograph stations. Vibration Direction Seismic Waves – Body Waves

  6. Surface waves behave likeS-waves in that they cause up and down and sideto side movement as they pass, but they travel slower than S-waves. Surface waves differ from body waves in that they do not travelthrough Earth’s interior, but instead travel along paths nearly parallel to the surface of Earth. Seismic Waves – Surface Waves

  7. Surface waves that cause horizontal shearing of the ground. They move in much the same way as a snake slithering across the ground. 1) Love Wave Surface waves are the most destructive and cause the most damage. Vibrate in a perpendicular direction compared to that of wave motion. Direction of Motion Seismic Waves – Surface Waves

  8. Surface waves that cause both horizontal (side-to-side) and vertical (up and down) movement within the ground. 2) Rayleigh Wave Most of the shaking felt from an earthquake is due to these waves and these waves are the most destructive and cause the most damage. Vibrate in a rolling motion in the same direction aswave motion. Direction of Motion Seismic Waves – Surface Waves

  9. P-waves, S-waves, and Surface waves are all recorded on the seismogram as seen below: These paper records are important when seismologist wants to locate the position of the epicenter of an earthquake. Seismologist can determine the difference in arrival times between the P-wave and the S-wave. Seismograph and Seismogram

  10. Seismic Waves - Comparison

  11. Example 1: Which description best describes p-waves? they move back and forth (compressional wave) and travel through any material. they move back and forth (compressional wave) and move only through solids. they move side to side (transverse wave) and only travel through liquids. they move side to side (transverse wave) and travel through any material. Which seismic wave is the first to reach a seismic station? primary wave B) love wave C) secondary wave D) rayleigh wave

  12. Example 2: Body waves consist of ________? Primary waves Secondary waves Love waves Both Primary and Secondary waves Which wave is the fastest and moves in a push-pull motion? (A) L (B) primary (C) S (D) Surface

  13. Your Turn . . . Take the time and complete the following questions . . .(Solutions to follow) Question: Contrast the characteristics of Primary and Secondary waves.

  14. Solutions . . . Question: Answer: P - wave Push - pull waves which vibrate in the same direction in which theymove. Fastest earthquake wave and is the first to arrive at seismograph stations. Pass through all states of matter, solids, liquids, and gases. S - wave Shake the particles which cause them to vibrate in a perpendicular direction totheir motion. Slower than P - wave and is the second earthquake wave to arrive at seismic stations. Pass only through solids.

  15. Summary . . . Overview of Points covered: • 2 Categories of Seismic Waves: • Body Waves • Primary • Secondary • Surface Waves • Love • Rayleigh

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