2. Earthquake Waves

3. Focus: point in Earth where energy is released Epicenter: point on surface above earthquake

4. Richter Scale measures magnitude of an earthquake - a magnitude 7 has 10x more ground movement than magnitude 6

5. Types of Seismic Waves – Primary waves (p waves) Fastest waves Can travel through any material – Secondary waves (s waves) Slower than P waves Can travel only through solids (no liquids) – Surface waves (l waves) Energy waves that reach the Earth’s surface Most damaging earthquake waves

6. Speed up when going through Denser material. These are the fastest waves!

7. These waves can only travel through solids. Slower than P-waves.

8. P wavesS waves Primary WavesSecondary Waves Travel faster, and at seismic stations first.Travel slower, and arrive at seismic stations second. Push-pull, or compression waves.Side-to-side, or shear waves. Travel through solids, liquids, and gases.Travel only through solids.

9. L – Waves Slowest waves Most destructive!!!

10. Earthquake Damage & Loss of Life Depend On: Earthquake magnitude Duration of ground movement Depth of focus Type of ground particles Building design Fire / Landslides / Tsunami Emergency and medical services Video on Haiti earthquake magnitude 7.0

11. Tsunami

12. Seismic risk in U.S.

13. Faults in North Carolina

14. Let’s Review…How do scientists know what the Earth’s interior is made of?

16. Moho Boundary Discovered in 1909 by Andriji Mohorovicic. Boundary between Crust & Mantle. Change in speed of seismic waves!!!

17. Remember, Earth is composed of layers

18. Liquid Outer Core: Iron-Nickel Liquid S waves stop at a depth of 2900 kilometers since they cannot travel through liquids P waves also slow down because less dense – Composed of liquid iron and nickel.

19. Inner Core: Solid Iron-Nickel Metal – P waves speed up

20. Seismograph – Device used to Measure Earthquake Waves

21. Seismogram – the record of the ground shaking made by a seismograph Determines: – Speed of Waves – Distance to earthquake’s epicenter

22. Seismogram Average time travel of P & S waves. Find time between P & S wave. Go vertically to find the distance from the epicenter.

23. Example to Do Together:

24. To find the Epicenter you need at least 3 stations distances! (triangulation)

25. Locating the epicenter of an earthquake Use distances of earthquake from three observatories. Use a compass Intersection of circles determines epicenter San Francisco Denver Tucson