How to focal mechanisms a review for Lab 12

1. How to focal mechanisms a review for Lab 12 Modified from online version created by Peter Polivka

2. On LOWER hemisphere projections the arc bows in the dip direction

3. How do things move? Compression (Black) moves away What type of fault is this? Is this left or right lateral?

4. What are each of these? How can you tell? Normal Reverse/Thrust Map view

5. To figure out the 2 alternate fault planes – start with one plane at a time

6. Connect the endpoints

7. Which way is the dip?

8. To measure dip: visualize stereonet

9. Rotate poles to strike line

10. Read off dip 0o 30o 60o ~77o 90o

11. 2 strike options – which one for R.H.R.? Option 2 Option 1

12. 2 strike options – which one for R.H.R.? Option 2 L R NO GOOD Option 1

13. 2 strike options – which one for R.H.R.? Option 2 CORRECT! R L Option 1

14. Read off the strike 0o 30o 330o ~298o 60o 300o Option 2 270o 90o 120o 240o 150o 210o 180o

15. Once one fault plane is complete, do the 2nd fault plane Striking 298o Dipping 77o Striking 190o Dipping 39o