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Earthquakes

Earthquakes. Earthquakes. An earthquake is a shaking of Earth’s crust caused by a release of energy. Earthquakes are often more destructive than volcanoes because the area affected can be greater. Earthquakes. More than 1 million earthquakes occur each year – that’s about 1 every 30 seconds.

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Earthquakes

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  1. Earthquakes

  2. Earthquakes • An earthquake is a shaking of Earth’s crust caused by a release of energy. • Earthquakes are often more destructive than volcanoes because the area affected can be greater.

  3. Earthquakes • More than 1 million earthquakes occur each year – that’s about 1 every 30 seconds.

  4. Death Tolls

  5. Causes of Earthquakes • The major cause of earthquakes is when stress builds up within Earth’s crust. • This stress occurs when plates move past each other.

  6. Normal Faults

  7. Reverse Faults

  8. Strike-slip Faults

  9. How Deep? • Most earthquakes occur between 30-700 km below the surface. • The type of plate boundary involved will determine the depth of the earthquake.

  10. How Deep? • Focus: The place inside the Earth where the earthquake actually occurs. • Epicenter: The point on Earth’s surface directly above the focus.

  11. Earthquake Waves • Body Waves: • Primary or P-waves • Secondary or S-waves • Surface Waves: • L-waves

  12. Body Waves • Travel through the body of the Earth. • P-waves: • Move back and forth (compression). • Can travel through any material. • Solid rock, magma, water, air.

  13. Body Waves • S-waves: • Move up and down. • Are almost twice as slow as P-waves. • Cannot travel through liquids.

  14. Surface Waves • When P and S waves reach the surface, they create an L-wave. • They resemble ripples on a pond and can travel about 3 km/h.

  15. Surface Waves

  16. Seismographs • The instrument used to record earthquake waves is called a seismograph. • A seismogram is the data recorded from the seismograph.

  17. Measuring an Earthquake

  18. Earthquake Magnitude • The scale used for earthquake magnitude is the Richter Scale. • The Richter Scale measures the amount of energy released by an earthquake.

  19. Magnitude 6.0

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