RSQSim

1. RSQSim Jim Dieterich Keith Richards-Dinger UC Riverside Funding: USGS NEHRP SCEC

2. Representation of Fault Friction • Constitutive relation: • State evolution: • Stress evolution: • Terms in red are additional ones due to normal stress variations (Linker and Dieterich, 1992) • Interaction coefficients, K, calculated from the dislocation solutions of Okada, 1992 • Tectonic stressing rates derived from backslipping the model • Numerical integration too slow for the scale of problems we would like to address

3. State 0: locked fault State 2: seismic slip Representation of Fault Friction • Constitutive relation: • State evolution: • Stress evolution: State 1: nucleation

4. Representation of Fault Friction • No predetermined failure stress or stress drop • Stress drop scales roughly as

5. Representation of Fault Friction • No predetermined failure stress or stress drop • Stress drop scales roughly as

6. Approximations to Elastodynamics Parameters that influence the rupture process: • Slip speed during coseismic slip determined from shear impedance considerations • Reduction of a on patches nearby to seismically slipping patches • Stress overshoot during ruptures

7. Effect of Overshoot on Rupture Characteristics Large overshoot (13%) Small overshoot (1%)

8. Approximations to Elastodynamics Values for rupture parameters determined by comparison with fully dynamic rupture models DYNA3D – Fully dynamic finite element simulation Propagation time 14.0 s RSQsim – Fast simulation Propagation time 14.3 s

9. Smooth Initial Stress (w/ block of higher normal stress)

10. Representation of Viscoelasticityafterslip • Rate-strengthening (a > b) patches • Approximated as always sliding at steady-state • Distributed as • Deep creeping extensions to major faults • Shallow creep on major faults • Entire creeping sections (e.g. SAF north of Parkfield) • Possibly with small imbedded stick-slip patches • More complicated mixed stick-slip and creeping areas (e.g. Hayward Fault)

11. Representation of Viscoelasticityafterslip Penetration of slip of large events into creeping zone

12. Representation of Viscoelasticityafterslip Fraction of moment release in creeping section Aftershocks

13. Representation of Viscoelasticityafterslip Small repeating earthquakes Simulation 1989 Loma Prieta Earthquake

14. Power-law temporal clustering Stacked rate of seismicity relative to mainshock origin time Decay of aftershocks follows Omori power law t -p with p = 0.77 Foreshocks (not shown) follow an inverse Omori decay with p = 0.92 Dieterich and Richards-Dinger, PAGEOPH, 2010

15. Power-law temporal clustering Interevent Waiting Time Distributions California Catalog 1911 – 2010.5

16. Power-law temporal clustering Space – Time Distributions

17. Earthquake cluster along San Andreas Fault M7.3 43 aftershocks in 18.2days All-Cal model – SCEC Simulator Comparison Project

18. Earthquake cluster along San Andreas Fault M6.9 Followed by 6 aftershocks in 4.8 minutes All-Cal model – SCEC Simulator Comparison Project

19. Earthquake cluster along San Andreas Fault M7.2 All-Cal model – SCEC Simulator Comparison Project

20. Colella et al., submitted Slow-slip events • slip ~2.3 - 4.0 cm • duration ~10-40 days • inter-event time - ~10-19 months • simultaneous slip in different areas • no Omori clustering • spontaneous segmentation

21. Summary or Conclusions (if appropriate or desired)