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Earthquakes

Earthquakes. Wave Motions Nelson’s Class. Wave: a wave is one of a series of movements passing along a surface or through a substance. A wave can travel through a material without the material itself traveling with the wave.

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Earthquakes

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  1. Earthquakes Wave Motions Nelson’s Class

  2. Wave: a wave is one of a series of movements passing along a surface or through a substance

  3. A wave can travel through a material without the material itself traveling with the wave. A wave can originate at one point and then travel outward in all directions. The waves of an earthquake travels outward in all directions from the point of origin, or focus.

  4. Vibrations from earthquakes travel in waves. Earthquake waves are known as seismic waves. Some earthquake waves travel through the body of the earth. These vibrations are called body waves.

  5. Seismic Waves At the top: Primary waves, also known as P-waves. P-waves are compressed waves. They compress and expand the material through which it travels. The wave vibrates parallel to the direction of the wave motion. This wave travels faster than the s-wave.

  6. Secondary waves: or S-Waves, shown at the bottom in the illustration S-waves travel slower than P-waves. S-waves are transverse earthquake waves. They vibrate perpendicular to the direction of the wave motion. They can move in all planes as they pass through the body of the earth, these waves move from side to side.

  7. Surface Waves: Travel on the earth surface or below it to a depth of 1000 km (621 miles) Surface waves are slower than body waves. Some produce an “up- and-down” rolling motion. Others can move material from side to side which causes more damage to buildings. Surface waves can cause buildings to separate from their foundations. Reinforcing foundations can decrease hazards caused by these waves.

  8. Ground motion All seismic waves produce ground motion (shaking, jolting). When P-waves reach the surface, they cause vertical shaking at the point of contact. Earthquake waves that shake the structure vertically are usually less destructive than those that shake horizontally. When S-waves reach the surface of the earth, they cause horizontal shaking at the point of contact. This causes more damage to buildings and other structures. The ground motion from S-waves and surface waves usually causes more damage to structures than P-waves. Earthquake waves radiate out in a sphere in all directions from the point of focus.

  9. Seismic waves from an earthquake are recorded on a seismogram using an instrument known as the seismograph. Measuring seismic waves

  10. Credits Information used in making this slide presentation can be found In the AMSTI Teachers’ resource book. Pictures were obtained from the internet This PowerPoint is to be used for teaching about Earthquakes.

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