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Chapter 10: Earthquakes

Chapter 10: Earthquakes. 10.1: How and Where Earthquakes Occur 10.2: Locating and Measuring Earthquakes 10.3: Earthquake Hazards 10.4: Studying Earth’s Interior. 10.1: How and Where Earthquakes Occur. Causes of Earthquakes

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Chapter 10: Earthquakes

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  1. Chapter 10: Earthquakes 10.1: How and Where Earthquakes Occur 10.2: Locating and Measuring Earthquakes 10.3: Earthquake Hazards 10.4: Studying Earth’s Interior

  2. 10.1: How and Where Earthquakes Occur • Causes of Earthquakes 1. Earthquake-The shaking of Earth's crust caused by a release of energy. 2. The cause of most major earthquakes is strain that builds up along faults.

  3. 10.1: How and Where Earthquakes Occur 3. Fault-A break in the lithosphere along which plate movement occurs. 4. Focus-The point at which first movement occurs during an earthquake. 5. Epicenter-The point on the earth's surface directly above the focus.

  4. 10.1: How and Where Earthquakes Occur • Body Waves 1. The energy from an earthquake is released in the form of waves. 2. Body Waves- Waves that travel from the focus to through the body of the earth.

  5. 10.1: How and Where Earthquakes Occur 3. P waves-Compression waves that squeeze and stretch rock material. They can travel through any material (water, magma, rock and air). 4. S waves- Shear waves that cause material to move at right angles to the direction of wave travel. They can travel through solids but not liquids or gases.

  6. 10.1: How and Where Earthquakes Occur C. Surface Waves 1. Earthquake waves that travel on the surface. 2. Appear when P and S waves reach the surface. 3. Cause the most damage. Why? 4. Two Types: Love and Rayleigh. Love waves move side to side. Rayleigh move in elliptical patterns. • Animations of earthquake waves • Examine P and S waves • Savage Earth: Restless Planet Because they are on the surface

  7. 10.2: Locating & Measuring Earthquakes • Seismograph 1. Detects and records waves produced by earthquakes. 2. Seismogram-A record sheet placed on a drum. The drum turns slowly and any movement is recorded on the paper. See page 217.

  8. 10.2: Locating & Measuring Earthquakes B. Interpreting a Seismogram 1. P waves arrive first, then S waves. 2. The farther the station is from the earthquake, the larger the separation between P & S waves lines. Why? More time to get ahead. It is like a race between two people at different speeds.

  9. 10.2: Locating & Measuring Earthquakes C. Locating the Epicenter • We can triangulate the epicenter by using three different seismic stations. See page 219.

  10. 10.2: Locating & Measuring Earthquakes D. Measuring an Earthquakes Magnitude • Magnitude-A measure of the amount of energy released in an earthquake. • The Richter Scale was developed in 1935. It measures the amount of energy released by an earthquake.

  11. 10.2: Locating & Measuring Earthquakes 3. An increase of one whole number is equal to a 31-fold increase in energy. Ex. Mag. 6 earthquake is 31 times more powerful than a Mag. 5 earthquake. • Build Your Own Seismograph

  12. 10.3: Earthquake Hazards • Damage from Earthquakes • Damage is not only caused by the shaking from the earthquake, but also by foundation failure, fire and tsunamis. • Liquefaction-Occurs when loose soil temporarily takes on some of the properties of a liquid. This causes buildings and roads to collapse.

  13. 10.3: Earthquake Hazards 3. Aftershocks-Series of small earthquakes that follow the initial quake. 4. Fire can cause substantial damage. It is usually triggered by ruptured gas lines. 5. Tsunamis-A huge ocean wave triggered by an earthquake. Can travel long distances at speeds up to 750 kph.

  14. 10.3: Earthquake Hazards • Preventing Earthquake Damage • Earthquake prone cities have special building codes to help prevent building collapse. • Monitoring equipment helps to continue learning what structures hold up the best during an earthquake.

  15. 10.3: Earthquake Hazards C. Earthquake Risk • Areas near plate boundaries are not the only areas at risk. • New Madrid, MO is located near several faults buried under large amounts of sediments.

  16. 10.3: Earthquake Hazards D. Predicting Earthquakes • Seismic Gaps- Areas where stress may be building up along a fault. • Scientists can predict at risk areas, but not specific locations or times.

  17. 10.4: Studying Earth’s Interior • The Shadow Zone • Changes in the speed and direction of P and S waves indicate changes in the composition and state of the earth's interior. • A shadow zone is created by these changes. Remember that S waves cannot travel through liquids. See page 228.

  18. 10.4: Studying Earth’s Interior B. The Moho • Boundary between the crust and the mantle. • Where the dense rock of the mantle meets the less dense rock of the crust. • Located about 32 km under continents and 5-10 km under the oceans. Why? The crust is thinner in the ocean.

  19. 10.4: Studying Earth’s Interior • Transition Zone • Region in the middle of the mantle where the densities of the upper and lower mantle vary. • This change is due to changes in pressure as depth increases.

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