1. EARTHQUAKES & PLATE TECTONICS

2. LOMA PRIETA 1989

3. COLUMBIA 1999

4. TURKEY

5. Three Important Questions
1. What is an Earthquake?
2. How do they occur?
3. Where are they found?

6. The shaking of the earth’s crust caused by a release of tremendous
What is an EQ?
The shaking of the earth’s crust caused by a release of tremendous
amounts of
energy.

7. EQ Terminology: 1. Focus: area where slippage first occurs.
2. Epicenter: point on earth directly above the focus
3. Seismic waves: energy released in the form of wave motions in all directions from the focus; 3 types!

9. 1. P waves: (Primary) travel the fastest & are the first to be recorded by a seismograph; they travel through liquids, solids & gases
2. S waves: (secondary) second fastest & travel ONLY through solids
3. L waves: (surface) slowest waves traveling over earth’s surface like ocean waves; most destructive

10. Three Seismic Waves:

11. Locating the EQ:
To help locate the earthquake we use an instrument that detects and records earthquake waves. It is called the seismograph.
By using the seismograph scientists can figure out when the first P & S waves from an earthquake arrive at the seismograph location.

13. Locating the EQ:
Since P waves travel faster than S waves, the P waves made by the EQ arrive first.
The farther the seismograph station is from the EQ, the larger the difference is in the arrival times for the P and S waves.

14. Locating the EQ epicenter:
To locate the epicenter, you need to take readings of epicenter distance from three different seismograph stations.

15. Locating the EQ epicenter:

16. Major Earthquake Zones
Three major zones: Ring of Fire Mid-Atlantic Ridge Eurasian-Melanesian Belt

18. 1. The Ring of Fire
Includes west coasts of North & South America and east coast of Asia
Forms ring around Pacific
Usually areas of subduction or fault zones

19. Convergent Boundary

20. 2. Mid-Atlantic Ridge
Earthquakes occur because oceanic crust is pulling away from the sides of the ridge (Divergent Boundary)

21. Divergent Boundary

22. 3. Eurasian-Melanesian Belt
Collision of the Eurasian plate w/ the African & Indian Plate
(Transform Boundary)
Forms huge mountain system

23. Transform Boundary

24. Wave Velocity
By using a seismogram scientists have been able to learn more about the layers of the earth.

25. Wave Velocity
Since P waves slow greatly at 2900 km and speed up again at 5000 km and S waves stop at 2900 we can conclude that the outer core begins at 2900 km and is made up of liquid material.

27. The Shadow Zone