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
Along the red line - Right lateral strike slip fault b/c the block you look at moves to your right
This would be left lateral along the alternate plane
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
What type of fault is this? oblique normal

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.?

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

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

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

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