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Recognizing faults

Recognizing faults. Practice with thrust faults and normal faults. Why study faults?. Classification of faults: - each type of fault forms under different geologic conditions - so, if we can characterize the nature of the fault, we can conclude something about the geologic history.

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Recognizing faults

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  1. Recognizing faults Practice with thrust faults and normal faults

  2. Why study faults? Classification of faults: - each type of fault forms under different geologic conditions - so, if we can characterize the nature of the fault, we can conclude something about the geologic history...

  3. Some faults are easy to see… • A Normal fault The San Andreas fault - a slip fault

  4. Death Valley (photo by M. Miller) Some are harder to see ……an extensional fault • The fault is here <===(normal fault) <======== The level land has dropped DOWN

  5. strike dip Orientation of fault surfaces: Strike and Dip Note: for mechanical reasons fault planes are seldom planar over long distances…thus, we must take MANY strike and dip measurements along a fault.

  6. Wytch Farm Oil Field, southern England (taken from Kttenhorn & Pollard, AAPG Bull, 2001) The Nature of Fault Shapes • Faults are not infinite • Faults can be irregularly shaped

  7. Strike Slip Fault

  8. http://earthobservatory.nasa.gov/Study/denali/

  9. Oldest fault Compression Newest fault

  10. Compression A thrust fault showing how layers have moved. (black is a layer of coal) Hanging wall Foot wall

  11. Compression: Distortion along a fault • Movement drags on the rock next to this thrust fault. • The layers became bent when the walls moved. Hanging wall Foot wall Fault

  12. Extensional faults (Utah)

  13. Extension • An area of extension is called Basin and Range topography. (the flat areas are basins, the mountains are ranges)

  14. Extension • The fault line is here Hanging wall This lower area has dropped down <==== Foot wall

  15. Extension • Normal faults Foot wall Hanging wall Foot wall Notice this broken layer has moved down.

  16. Extension • Can you see a normal fault in this picture? Hanging Wall The black shale layer has dropped down compared to the other side. Foot Wall http://raider.muc.edu/~mcnaugma/structur.htm

  17. Hanging wall #1 Is this a normal or thrust fault? Foot wall http://virtual.yosemite.cc.ca.us/ghayes/Death_Valley_Friday.htm

  18. #2 Is this a normal or thrust fault? Hanging wall (Same layer) Foot wall http://raider.muc.edu/~mcnaugma/structur.htm

  19. #3 Is this a normal or thrust fault? Hanging wall (older rock) (younger rock) Foot wall http://raider.muc.edu/~mcnaugma/structur.htm

  20. #4 Normal or Thrust fault? www.pitt.edu/.../7Structures/NormalFaults.html

  21. #5 Normal or thrust fault? http://gpc.edu/~pgore/geology/geo101/faults.htm

  22. #6 Thrust or Normal faults?

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