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Grand Inversion Dsr: How do ruptures end and how do they scale with length?

Grand Inversion Dsr: How do ruptures end and how do they scale with length?. Tour of some mapped ruptures Focus on ruptures with multiple sections Ask, What do they say about how fault-to-fault slip transfers? What do the existing ruptures say about how gaps between faults are filled?

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Grand Inversion Dsr: How do ruptures end and how do they scale with length?

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  1. Grand Inversion Dsr: How do ruptures end and how do they scale with length? • Tour of some mapped ruptures • Focus on ruptures with multiple sections • Ask, What do they say about how fault-to-fault slip transfers? • What do the existing ruptures say about how gaps between faults are filled? • How does AD scale in sections of a multi-fault rupture?

  2. Exceptional case: M6.6 slip >> M7.1

  3. Does not reflect adjustments at the Denali-Totchunda intersection; displacement taper at intersection would be less clear.

  4. Average Displacement vs. Surface Rupture Length Wells and Coppersmith Ask where the subfaults would plot in AD-SRL...

  5. Plot section AD vs. length Strike-slip events with subsegments in Wesnousky 2008. Proposed smaller AD increase with length (solid line) makes the separation clearer.

  6. Non-strike-slip events

  7. All Ruptures Sub-section average and maximum displacements plot above expectations for their length. Somehow most sections adjust their displacements to the final event size. Dsr displacements have to be assigned after any fault-to-fault links are done

  8. Provisional Conclusions • Dsr scales with full rupture length • Fault-to-fault jumps are not simply links of sub-segments - component displacements are generally too large • One interpretation: The stress being relieved in a rupture is a regional property, and relatively insensitive to stress states at step-overs.

  9. Observation-Based Probabilities of Step-Overs • Or, “The Length to Which an Earthquake Will Go to Rupture” • (Wesnousky, Biasi, in press)

  10. Data: Wesnousky (2008) surface ruptures having reasonable geologic mapping • Consider only strike-slip ruptures (22 total) • Step-overs counted if 1 km or more.

  11. Event number from Wesnousky, 2008 Curiosity: # of step-overs is not a function of rupture length. Maybe long faults have worked out step-overs in the process of growing long.

  12. Number of stepovers per rupture modeled by Poisson and Geometric distributions Poisson: stepover is random w/in rupture (rupture ignores steps) Geometric: steps have probability of crossing (51%). Fit quality is equal between them.

  13. Step-overs and Multi-Fault Ruptures • Approximately even chance in present data set that rupture would include one or more step-overs of one km or larger. • Geologic considerations favor the geometric probability model

  14. Ask given the rupture extent, what displacement can we predict given some distance the end of the fault? Normalize by length and average displacement, then calculate the mean and standard deviation.

  15. Distribution of normalized slip as a function of distance from the end of the rupture

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