1. Earthquakes

2. What is an Earthquake? Natural rapid shaking of the lithosphere
Caused by: a release of energy stored in rocks
The energy creates waves that travel through Earth!

3. Seismic Waves 1. Radiate out from the EQ’s focus
2. Waves are energy in motion!

4. Focus & Epicenter 3. The focus is the EQ’s center underground
4. The epicenter is the point on Earth’s surface directly above the focus

6. Crest
Wavelength λ
Trough

7. Do we have great risk of eq damage? Why?
No. New York is in the middle of a plate.

8. Elastic Rebound Theory
Pressure builds up
Rock reaches elastic limit
Rock layers break (EQ)

9. Body Waves
P and S seismic waves: They travel through the body of the Earth

10. P-waves Primary, pressure, push-pull
Travel fastest of the seismic waves, travel through solids and liquids

11. S-Waves Secondary, shaking, shear, side to side
Travel through solids only!

12. Surface Waves
Seismic waves that only travel on the Earth’s surface, slowest waves!

13. The Shadow Zone S-waves can NOT travel through the liquid outer core
P-waves are bent (refracted) as they pass through the liquid outer core
This is why EQ’s are not felt in certain areas of the Earth.
Shadow Zone: No P- or S-waves!

15. Seismograph: Instrument detects and records EQ’s
Seismogram: Record sheet of an EQ

16. Finding the Epicenter Need 1 seismogram from 3 different places
Use your time-travel graph to find the distance to the epicenter (ESRT pg. 11)

17. Draw circles around your seismic stations at those epicenter distances
Where the 3 circles meet is your EQ

18. Tsunami
Seismic sea wave – often greater than 100 ft high and can travel at 100’s of mi/hr!
9.0 EQ Japan March 2011

19. Earthquake Intensity Richter Scale: measures EQ magnitudes.
Measures the height of the largest waves on the seismogram.
Modified Mercalli Scale: measures EQ intensity by describing amount of damage.

22. Mountain Building Fault – fracture along which movement has occurred.
Where EQ’s happen!

23. Strike-Slip Fault
Crust slides on each side
Orange Grove in CA

24. Normal Fault “slides down” Tensional fault – pulled apart
Breakdown – rock slides down
Occur at divergent boundaries

25. Reverse Fault “pushed up” Pressure – pushed together Rock layers snap!
Pushed up slope
Occur at convergent boundaries

26. Folds - when rocks don’t break they bend.
Caused by compression - bends rock into series of troughs and arches
Convergent boundaries

27. Syncline
Syncline – valley/trough, youngest in middle

28. Anticline
Anticline – hill/arches, oldest in the middle

29. Tectonic Domes
Sometimes rock layers can be uplifted into a dome shape.
Magma intrusion

30. Where would the oldest rocks exposed at the surface be?
In the middle.