1. Chapter 19 - Earthquakes
19.1- Forces within Earth

2. 1/5/16, Tuesday To-Do Bellringer: What causes Earthquakes?
Get a copy of the Learning Target Inventory off of the front stool. Rate yourself on each learning target.
If you have not taken your semester 1 exam yet, I’ll be giving it to you tomorrow.

3. 1/5/16 Tuesday
Often, you may hear people say that the animals and fish seemed to sense there is an earthquake coming. Why/how do you think that may be possible?

4. To-Do 1/4/16, Monday
Bellringer: What would you do during an earthquake?

5. Bellringer: 1/6/16 Wednesday
*Define what you think Stress and Strain is as they apply to rocks.
Get a copy of the guided notes off of the front stool.
We’ll Finish reviewing earthquake safety and take notes on stress and strain.

6. Earthquakes: Earthquake = vibrations caused by movement in crust
Are the result of movement of crust produced by Plate tectonics
Stress = total force acting on crustal rocks
Builds up overtime
Overcomes strength of rocks and causes movement along fractures in rock

7.
Stress
Three types
Compression – decrease volume of material
Tension – pulls material apart
Shear – causes material to twist
Strain = deformation of material in a response to stress

8. Deformation
Elastic – when a material is compressed, bent, or stretched
at low stress
Material can return to “normal” when stress is zero
Example: Pulling on a rubber band

9. Deformation Plastic – stress builds up past elastic limit
Permanent deformation – stays changed even when stress is zero
Point of Rupture = failure
Example: Pulling rubber band until it breaks

10. Deformation
Most materials exhibit varying degrees of plastic and elastic deformation

11. Bellringer:
Compare and contrast the movements of each of the three types of faults. Page 531 in your book.

12. Faults notes:
Any fracture or system of fractures along which Earth moves
Happens along weak regions
Fault plane = surface along which movement takes place

13. Fault Animation:
Fault Motion:
Examine animations of fault motion:

14. What kind of fault is it?

15. Fence offset produced by 1906 San Francisco earthquake Right-Lateral Strike-Slip Faults The fence was offset 2.6 m by the magnitude 8.2 earthquake of April 18, 1906, San Francisco, California. The section of the San Andreas fault shown here is 0.8 km north of Woodville. The photo is looking northeast. The lateral or strike-slip fault offset is large; however, the trace is nearly invisible. This earthquake, together with the fire that followed, resulted in more than 3,000 deaths and 400 million dollars of property damage. [Photo credit: G.K. Gilbert, U.S. Geological Survey. Photo has been colorized.] 

16. What kind of fault is it?

17. The footwall is on the left
The footwall is on the left. Since the beds indicate that the hanging wall has risen relative to the footwall, this is a reverse fault.

18. What kind of fault is it?

19. If you stood on the fault plane, the block on the right would be under your feet. This is thus the footwall. The red line marks equivalent layers on opposite side of the fault. Since the hanging wall dropped relative to the footwall, this is clearly a normal fault.

20.
Faults
Reverse Fault – form as a results of horizontal and vertical compression that squeezes rock
Seen near convergent plate boundaries
Two areas end up closer together after faulting

21. Faults Normal fault – movement partly horizontal and partly vertical
Faults
Normal fault – movement partly horizontal and partly vertical
Horizontal movement pulls rocks apart and stretches crust
Vertical movement causes one side of rock to move down relative to the other side
Two areas end up farther apart after faulting

22. Faults Strike-slip fault – caused by horizontal shear
Faults
Strike-slip fault – caused by horizontal shear
Movement is mainly horizontal in opposite direction
Example: San Andreas Fault
Creates offset features after movement

23. Discuss:
Evaluate how earthquake intensity is related to the type of fault.

24. Bellringer:
Contrast the three types of seismic waves.

25. Earthquake waves
Seismic waves = vibration of the ground produced during an earthquake
Primary waves = squeeze and push rocks in same direction wave is traveling
Secondary waves = cause rocks to move at right angles relative to wave direction
Slower than P waves
Surface waves = cause most destruction and take longest to past
Slowest wave, only travel of Earth’s surface

26. Seismic Waves

27. Earthquake Focus = point where waves originate
Epicenter = point on surface directly above focus

28. In-Class Assignment/Homework