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Dynamic Issues in Fault-to-Fault Jumping

Dynamic Issues in Fault-to-Fault Jumping. David Oglesby UC Riverside UCERF3 Workshop June 11, 2011. Basic Idea. What are some properties that affect the ability of rupture to jump a stepover? Can we still predict jump likelihood ahead of time?. Mechanism of Jumping Rupture.

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Dynamic Issues in Fault-to-Fault Jumping

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  1. Dynamic Issues in Fault-to-Fault Jumping David Oglesby UC Riverside UCERF3 Workshop June 11, 2011

  2. Basic Idea • What are some properties that affect the ability of rupture to jump a stepover? • Can we still predict jump likelihood ahead of time?

  3. Mechanism of Jumping Rupture

  4. Mechanism of Jumping Rupture Harris and Day, 1993

  5. Effect of Stepover Width, Direction, and Overlap/Gap Harris and Day, 1993

  6. Effect of Static Stress Level Harris and Day, 1993

  7. Effect of Multiple Earthquake Cycles on Stress 4 km Wide Compressional Stepover Duan and Oglesby (2006) Stress (Mpa) Along Strike (km)

  8. Effect of Stress/Slip Gradient at Fault Edge Oglesby, 2008

  9. Effect of Stress/Slip Gradient at Fault Edge Elliott et al., 2009

  10. Effect of Stress/Slip Gradient at Fault Edge Elliott et al., 2009

  11. Linking Faults Magistrale and Day,1999

  12. Linking Faults Lozos et al., 2011

  13. Intermediate Faults Lozos et al. 2011 No intermediate fault

  14. Intermediate Faults 3 km long intermediate fault

  15. Intermediate Faults 5 km long intermediate fault

  16. Intermediate Faults 7 km long intermediate fault

  17. Intermediate Faults 10 km long intermediate fault

  18. Intermediate Faults 15 km long intermediate fault

  19. Frictional Properties • Fracture energy determines area of critical slipping region on secondary fault segment for nucleation. • Higher fracture energy -> harder to nucleate rupture on secondary fault segment.

  20. Summary • Fault geometry • Extensional stepovers (with overlaps!) are easier to jump than compressional ones. • Narrower stepovers with overlaps facilitate jump. • With linking faults, smaller angles and shorter connecting segments facilitate jump. • Intermediate faults can facilitate or inhibit jump depending on size. • Stress field • Stress near failure, with strong stress gradient at edge of fault, facilitates jump. • Frictional Properties • Friction law is secondary effect; low fracture energy facilitates jump.

  21. Conclusions • There are many factors that influence whether rupture will jump a stepover, and what the slip will be on that fault system. • We have only scratched the surface! • Some factors may be known ahead of time [geometry, surface slip in past event(s)], some not. • Dynamic (vs. static) analysis may be necessary in some cases. • What is the predictability? • Do the current results imply that a specific model of each stepover is necessary? • Are there rules of thumb? • Better knowledge of stress field around stepover is crucial, as is subsurface geometry. • The observational results are telling us something about the physical parameters (geometry, stress, friction) on real faults.

  22. Effect of Overlap vs. Gap Harris and Day, 1993

  23. Slip in Multi-Segment Rupture Willemse et al., 1996

  24. Slip in Multi-Segment Rupture Willemse et al., 1996

  25. Slip in Multi-Segment Rupture Kase, 2010

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