Geology 360 - Introduction to Strike-Slip Faults

1. Geology 360 - Introduction to Strike-Slip Faults

2. Levant Strike-Slip Faults Left-lateral strike-slip Levant fault, plate boundary between Arabia and Africa

3. San Andreas from Space • Two northwest-southeast-trending faults are visible. • The Hayward Fault, bordering the urban area east of San Francisco Bay • The San Andreas Fault, crossing the mid-San Francisco Peninsula before dipping beneath the Pacific Ocean and surfacing again northwest of Golden Gate Bridge San Francisco Bay, California.

4. San Andreas fault, western North America

5. Outline • Stick-Slip and Creep • Andersonian Theory • Kinematics • Strike-Slip Faults on Continental Margins • Strike-Slip Faults on Mid-Ocean Ridges

6. Stick-Slip: Elastic Rebound Theory D

7. Elastic Rebound Theory • Imagine a fence across an active fault

8. Elastic Rebound Theory • Imagine a fence across an active fault • Regional deformation occurs but the fault does not break. The fence becomes curved.

9. Elastic Rebound Theory • Imagine a fence across an active fault • Regional deformation occurs but the fault does not break (locked fault) • Once the fault breaks, the fence is sheared in half and marks offset • The far-field strain may limit whether the fault accommodates all the plate motion at its trace

10. Elastic Rebound Theory

11. Elastic Rebound Theory

12. Creep (Aseismic Slip) • Imagine a fence across an active fault • Slip occurs slowly on the fault continually over time (fault is not locked) • Creeping faults do not store elastic energy that might be released by a stick-slip event (an earthquake)

13. Andersonian Theory

14. Conjugate Strike-Slip Faults

15. Determining Sense of Slip

16. Right-Lateral (Dextral)

17. Left-Lateral (Sinistral)

18. Arrow Heads ( ) and Tails ( ) Block moving toward you like an arrowhead heading towards you Block moving away from you like seeing the feathers of an arrow

19. Arrow Heads ( ) and Tails ( ) Right-lateral or left-lateral?

20. Arrow Heads ( ) and Tails ( ) Left-lateral

21. Arrow Heads ( ) and Tails ( ) Sinistral or Dextral?

22. Arrow Heads ( ) and Tails ( ) Dextral

23. Strike-Slip Faulting: Shallow Brittle vs Deep Shear

24. Strike-Slip Faulting: EQ’s = dislocations http://www.data.scec.org/Module/links/landrupt.html Landers rupture propagation movies

25. Strike-Slip Faulting: EQ’s = dislocations

26. Strike-Slip Faulting: EQ’s = dislocations

27. Strike-Slip Faults on Continental Margins 50 m N What is the sense of slip?

28. Strike-Slip Faults on Continental Margins 50 m N Right-lateral (dextral)

29. Transtension

30. Development of a Pull-Apart Basin

31. Pull-Apart Basin

32. Initial Releasing Bend

33. Evolution of a Releasing Bend

34. Normal (-) Flower Structure - Tulip

35. Transpression

36. Development of a Restraining Bend

37. Development of a Restraining Bend

38. Initial Restraining Bend

39. Evolution of a Restraining Bend

40. Reverse (+) Flower Structure - Palm

41. Summary of Flower Structures - Palms & Tulips

42. Summary of Step Overs - Strike-Slip Faults

43. Los Angeles - Pull apart structure Releasing bend

44. Summary of Flower Structures - Palms & Tulips

45. Summary of Flower Structures - Palms & Tulips

46. Summary of Flower Structures - Palms & Tulips

47. Summary of Flower Structures - Palms & Tulips

48. Oceanic Strike Slip fault: Transforms

49. Strike-Slip Faults on Mid-Ocean Ridges What is the sense of slip?

50. Strike-Slip Faults on Mid-Ocean Ridges Right-lateral (Dextral)