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Earthquake Basics

Earthquake Basics. Deadliest and Largest Earthquakes. Did You Know?. The swimming pool at the University of Arizona in Tucson lost water from sloshing caused by the 1985 M8.1 Michoacan, Mexico earthquake 2000 km (1240 miles) away. . Focus, Epicenter, and Fault. What Is an Earthquake?.

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Earthquake Basics

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  1. Earthquake Basics

  2. Deadliest and Largest Earthquakes

  3. Did You Know? • The swimming pool at the University of Arizona in Tucson lost water from sloshing caused by the 1985 M8.1 Michoacan, Mexico earthquake 2000 km (1240 miles) away.

  4. Focus, Epicenter, and Fault

  5. What Is an Earthquake? • An earthquake is the vibration of Earth produced by the rapid release of energy • Focus - point within Earth where the earthquake starts • Epicenter - location on the surface directly above the focus • Faults – fractures where movement has occurred

  6. What Is an Earthquake? • aftershock – • small • follows the main quake • foreshock – • small • precedes a major quake

  7. Types of Faults • Reverse (thrust) faults • Formed from pushing

  8. Types of Faults • Reverse (thrust) faults

  9. Types of Faults • Normal faults • Formed from pulling.

  10. Types of Faults • Strike-slip faults • Formed from sliding

  11. Types of Seismic Waves • Primary waves or P-waves • Squeeze and pull rocks in the same direction the waves are traveling • Travel through solids, liquids, and gases • Fastest

  12. Types of Seismic Waves • Secondary waves or S-waves • Travel along Earth’s outer layer • Shake particles at right angles to the direction that they travel • Travel only through solids

  13. Types of Seismic Waves • Surface waves • Travel along Earth’s surface, • Move in two directions as they pass through rock

  14. Measuring Earthquakes

  15. Measuring Earthquakes • Seismographs or seismometer • record earthquake waves • Seismograms • traces (graphs) of electronically recorded ground motion

  16. Measuring Earthquakes

  17. Earthquake Magnitude • Magnitude is the measure of the amount of energy released during an earthquake. • Richter scale • Based on the amplitude of the largest wave. • Does not estimate adequately the size of very large earthquakes

  18. Earthquake Magnitude • The moment magnitude scale • Widely used by seismologists • Considers: • the size of the fault rupture • the amount of movement along the fault • the rocks’ stiffness • Measures very large earthquakes

  19. Earthquake Magnitudes

  20. Earthquake Intensity • Modified Mercalli scale • measures the amount of damage (intensity) • uses the Roman numerals I to XII to designate the degree of intensity

  21. Earthquake Intensity

  22. Destruction from Earthquakes • Damage depends on: • the intensity and duration of the vibrations • the nature of the material on which the structure is built • the design of the structure

  23. Earthquake Damage

  24. Predicting Earthquakes • Predicting Earthquakes?? • Umm, nope

  25. Locating Earthquakes

  26. Locating Earthquakes • Earthquake Distance • The epicenter is located using the difference in the arrival times between P and S wave recordings, which are related to distance. • Earthquake Direction • Travel-time graphs from three or more seismographs can be used to find the exact location of an earthquake epicenter.

  27. Locating Earthquakes

  28. Locating an Earthquake

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