You Need the Following:

1. You Need the Following: • Papers on the Table • SCIENCE BOOK! • Sheet of Paper • Turn in your Test Self-Assessment • Turn in any test corrections

2. Earthquakes

3. What is an Earthquake? • Earthquakes: Vibrations (seismic waves) within Earth materials are produced by the rapid release of energy • Earth’s crust is in constant motion because of tectonic forces • Earth’s crust can store elasticenergy • When forces exceed the elastic limits and structural strength of the rocks, the rocks will break and/or move producing vibrations that travel outward in all directions

4. Earthquakes • The actual place underground where the rocks break producing vibrations is called the focus • The place on the surface directly above the focus is called the epicenter

5. How Earthquakes Occur

6. What types of forces are created? Tension Force: • stretching or pulling force • Makes a normal fault

7. Normal Fault http://www.geo.uib.no/jordskjelv/index.php?topic=earthquakes&lang=en

8. What types of forces are created? Compression Force: • force pushing something together • Makes a reverse fault

9. Reverse Fault http://www.geo.uib.no/jordskjelv/index.php?topic=earthquakes&lang=en

10. What types of forces are created? Shear Force: • a system of forces that operates against a body from different sides • Makes a strike-slip fault

11. Strike-Slip Fault http://www.geo.uib.no/jordskjelv/index.php?topic=earthquakes&lang=en

12. Types of Faults Overview

13. Do the Following: • Turn in your What are Earthquakes? Directed Reading • Fill out your Agenda • Get out your Earthquake Notes • Make sure you have your SCIENCE BOOK!

14. What Causes Earthquakes? • Movement along faults: occurs when the energy exceeds the friction holding the sides of the fault together and is suddenly released. • Movement of magma (volcanic) • Volcanic eruptions

15. Seismic Waves Originate at the focus and travel outward in all directions • Foreshocks: small earthquakes that come before a major earthquake • Aftershocks: Are adjustments in the crust after in earthquake • Smaller than main earthquake, but can cause as much or more damage. They can continue for weeks to months. Not every earthquake produces aftershocks

16. Seismic Waves

17. 3 Types of seismic Waves • P waves (primary waves) Compressional wave • Particles move back and forth in the same direction as the wave • Travels the fastest • Can pass through solids and liquids (gases also) • Does not cause damage

18. Types of Waves • S wave (secondary wave, shear wave) • Particles move at right angles to the direction of the wave • Travels slower than P waves • Can pass through solids only • Does not cause damage

19. Types of Waves • L wave (long wave, surface wave, ground wave) • Particles move in elliptical orbit • Originates on the surface after the P and S waves go straight up from the focus and reach the surface • The L wave causes the damage and will be the strongest at the epicenter • Travels the slowest

20. How Do We Measure Earthquakes? Earthquake waves are recorded by a seismograph and the recording of waves on paper is called seismogram

21. How Do We Measure Earthquakes? • Intensity – a measure of the effects on an earthquake at a particular location • Magnitude: a measure of the strength or amount of energy released during an earthquake

22. How Do We Measure Earthquakes? • Richter Scale: Measures the amplitude of earthquake waves on seismograms • Scale from 1-10 • Each number is 10 times the amplitude of the number below

24. Do the Following: • Get out your Earthquake Notes • Make sure you have your SCIENCE BOOK!

25. Earthquake Dangers • Most injuries and deaths are caused by falling objectsand most property damage results from fires that start • Tsunami: seismic sea wave sometimes generated when an earthquake originates on the ocean floor

27. Tsunami—December 2004 http://www.bedford.k12.ny.us:16080/flhs/science/images/tsunami2004/

29. Earthquake Dangers • Seiche: rhythmic sloshing of small bodies of water A seiche is the sloshing of a closed body of water from earthquake shaking. Swimming pools often have seiches during earthquakes.

30. Earthquake Dangers • Liquefaction: unconsolidated materials that are water saturated may turn to a fluid causing some underground objects such as storage tanks to float to the surface Ground fissures caused by liquefaction near the mouth of the Pajaro River in California during the 1989 Loma Prieta earthquake. When the surface of the ground oscillates, wet, sandy, and muddy soils can flow like a liquid. This is liquefaction. You can liquefy wet sand at the beach by pumping it up and down with your feet. Photo courtesy of the Loma Prieta Collection, Earthquake Engineering Research Center, UC Berkeley.

31. Earthquake Dangers • Landslides

32. Earthquake Safety • Protect yourself from falling objects (GET UNDER SOMETHING) or stand in a hallway or doorway (watch out for a swinging door) • Do not try to go outside during the earthquake • After the earthquake and before the aftershocks, go outside • Do not return to the building until it has been inspected