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Chapter 8

Chapter 8. Earthquakes and Earth ’ s Interior. Section 8.1. What is an Earthquake?. What is an earthquake?. An earthquake is the vibration of Earth produced by the rapid release of energy. Example: 1906 San Francisco Earthquake.

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Chapter 8

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  1. Chapter 8 Earthquakes and Earth’s Interior

  2. Section 8.1 What is an Earthquake?

  3. What is an earthquake? • An earthquake is the vibration of Earth produced by the rapid release of energy. • Example: 1906 San Francisco Earthquake. • Earthquakes usually occur when rocks under stress suddenly shift along a fault. • Stress: A force that can change the size and shape of rocks. • Fault: Fractures in the Earth where movement occurred. • The area along a fault where slippage first occurs is called the focus of an earthquake. • The point on the earth’s surface directly above the focus is called the epicenter. • When an earthquake occurs, seismic waves radiate outward in all directions from the focus.

  4. What is an earthquake?

  5. A fault is • A place on Earth where earthquakes cannot occur. • A fracture in the Earth where movement has occurred. • The place on Earth’s surface where structures move during an earthquake. • Another name for an earthquake.

  6. An earthquake’s epicenter is • The place on the surface directly above the focus. • A spot halfway between the focus and the surface. • The spot below the focus. • Any spot along the nearest fault.

  7. When an earthquake occurs, energy radiates in all directions from its source, which is called the • Epicenter. • Focus. • Fault. • Seismic Center.

  8. Earthquakes are usually associated with • Violent weather. • Faults. • Large cities. • The east coast of North America.

  9. What is an earthquake? • Geologists explain many earthquakes by the elastic rebound hypothesis. • This hypothesis states that when the stress in rocks becomes to great, they fracture, separate, and spring back to their original shape, or rebound. • As they fracture and slip into new positions, rocks along a fault release energy in the form of vibrations called seismic waves.

  10. What is an earthquake?

  11. Which of the following causes earthquakes? • Elastic Rebound. • Richter Scale. • Release of Heat. • Frictional Heating.

  12. The hypothesis that explains the release of energy during an earthquake is called the • Richter Hypothesis. • Moment Magnitude Hypothesis. • Vibration Hypothesis. • Elastic Rebound Hypothesis.

  13. Most earthquakes are produced by the rapid release of which kind of energy stored in rock subjected to great forces? • Chemical • Thermal • Elastic • Mechanical

  14. During an earthquake, the ground surface • Moves only in a horizontal direction. • Moves only in a vertical direction. • Can move in any direction. • Does not move.

  15. What is an earthquake? • This release of energy often increases the stress in other rocks along the fault, causing them to fracture and spring back. • This reaction is the reason that major earthquakes are usually followed by a series of smaller tremors called aftershocks. • These aftershocks are usually much weaker than the main earthquake, but they can sometimes destroy structures weakened by the main quake.

  16. What is an earthquake? • Small earthquakes called foreshocks often come before a major earthquake. • These can happen days or even years before the major quake. • The San Andreas Fault is the most studied fault system in the world. • Studies have shown that displacement has occurred along segments that are 100 to 200-kilometers long (63 to 125-miles). • Some segments move slowly, which is known as fault creep. • Other segments regularly slip and produce small earthquakes. • Some segments stay locked and store elastic energy for hundreds of years before they break and cause great earthquakes.

  17. The adjustments of materials that follow a major earthquake often generate smaller earthquakes called • Foreshocks. • Surface waves. • Aftershocks. • Body waves.

  18. Major earthquakes are sometimes preceded by smaller earthquakes called • Aftershocks. • Focus shocks. • Surface waves. • Foreshocks.

  19. The slow continuous movement that occurs along some fault zones is referred to as • Slip. • Creep. • Fracture. • A foreshock.

  20. Small foreshocks that precede a major earthquake occur • From the day of the major earthquake to days after the earthquake. • Only on the day of the major earthquake. • Days or years before the major earthquake. • Only on the day before the major earthquake.

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