1. Investigating Faults With Models
Inquiry 15.3
Investigating Faults With Models

2. PROCEDURE
Discuss with your group what you already know about faults. What questions do you have about faults?
Look at the Fault Laboratory. You will use this model to investigate movement along a fault where blocks of rock slide past one another. What do you think will happen when a force is applied to the blocks? Discuss your hypothesis with your group.

3. 3. Work with your group to design an experiment that demonstrates how frictional resistance along a fault affects how rock moves during an earthquake. Record the materials and procedure you will use, how you will control all variables except the one you are testing, what you will look for, and what you will measure.
4. Note that you will con- duct trials with no Velcro strips and with one, two, and three strips.

4. 5. Collect your materials. Use Figure 15
5. Collect your materials. Use Figure 15.8 to set up your Fault LaboratoryTM. Check that each of the following steps is completed:
a. Carefully place the block with the hole so that the long strip of soft, looped Velcro is facing the “fault.” Use the bolt, washers, and wing nut to fix, or secure, the block with the hole to the box.
b. Notice how each side of the block has a different number of strips of “hooked” Velcro. For each test, you will rotate the block so there is more hooked Velcro (or frictional resistance) between the two blocks.

5. C. Slide the solid block (with no hole) in place next to the fixed block. Make certain the soft loop Velcro on both blocks is touching and secure. Use one to two tongue depressors as spacers between the tote tray and solid, unfixed block only if the blocks are loose. This will push the blocks together
D. Make a loop or tightly knot the cord to the hook on the solid, unfixed block.
E. Use a loop or tightly knot the cord to the spring scale.

6. 6. Pull on the spring scale, which will apply a sliding force to the unfixed block. How much force do you have to apply to the block before the fault ruptures (that is, before the block moves abruptly)? Record the maximum force in your data table under “0,” since you are not using any hooked Velcro on the blocks, and there is very little frictional resistance along your fault. Conduct three trials.

7. 7. Now rotate the unfixed block so there is one strip of hooked Velcro along the fault. Repeat Procedure Step 6. Conduct three trials. Record your force data each time under “1” in your notebook.
8. Now repeat procedure with two strips of hooked Velcro, recording data under “2” in your notebook.
9. Finally, rotate the block again and test the force using three strips of hooked Velcro. Repeat procedure and conduct three trials. Record your data under “3” in your notebook.
10. Reset block fixed block to “0” side and clean up.

8. REFLECTING ON WHAT YOU’VE DONE
How did the amount of friction along the fault affect the amount of force needed to rupture the fault? Use data to support your answer.
B. Under what conditions did the blocks rupture more abruptly?
C. Under what conditions did the block slip (move slowly) but not rupture?

9. D. Is there any sign on the earth’s surface that the earth is moving slowly beneath the crust? (Look at Figure 15.9 and use the caption to answer this question.)
E. How would you define the word “fault?”