1. 16/9/2011UCERF3 / EQ Simulators Workshop RSQSim Jim Dieterich Keith Richards-Dinger UC Riverside Funding: USGS NEHRP SCEC

2. 26/9/2011UCERF3 / EQ Simulators Workshop 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. 36/9/2011UCERF3 / EQ Simulators Workshop Representation of Fault Friction Constitutive relation: State evolution: Stress evolution: State 1: nucleation State 0: locked fault State 2: seismic slip

4. 46/9/2011UCERF3 / EQ Simulators Workshop Representation of Fault Friction No predetermined failure stress or stress drop Stress drop scales roughly as

5. 56/9/2011UCERF3 / EQ Simulators Workshop Representation of Fault Friction No predetermined failure stress or stress drop Stress drop scales roughly as

6. 66/9/2011UCERF3 / EQ Simulators Workshop 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. 76/9/2011UCERF3 / EQ Simulators Workshop Effect of Overshoot on Rupture Characteristics Large overshoot (13%) Small overshoot (1%)

8. 86/9/2011UCERF3 / EQ Simulators Workshop Approximations to Elastodynamics Values for rupture parameters determined by comparison with fully dynamic rupture models DYNA3D – Fully dynamic finite element simulation RSQsim – Fast simulation Propagation time 14.0 s Propagation time 14.3 s

9. 96/9/2011UCERF3 / EQ Simulators Workshop Smooth Initial Stress (w/ block of higher normal stress)

10. 106/9/2011UCERF3 / EQ Simulators Workshop Representation of Viscoelasticity afterslip 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. 116/9/2011UCERF3 / EQ Simulators Workshop Representation of Viscoelasticity afterslip Penetration of slip of large events into creeping zone

12. 126/9/2011UCERF3 / EQ Simulators Workshop Representation of Viscoelasticity afterslip Fraction of moment release in creeping section Aftershocks

13. 136/9/2011UCERF3 / EQ Simulators Workshop Representation of Viscoelasticity afterslip 1989 Loma Prieta Earthquake Simulation Small repeating earthquakes

14. 146/9/2011UCERF3 / EQ Simulators Workshop Power-law temporal clustering 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 Stacked rate of seismicity relative to mainshock origin time

15. 156/9/2011UCERF3 / EQ Simulators Workshop Power-law temporal clustering Interevent Waiting Time Distributions California Catalog 1911 – 2010.5

16. 166/9/2011UCERF3 / EQ Simulators Workshop Power-law temporal clustering Space – Time Distributions

17. 176/9/2011UCERF3 / EQ Simulators Workshop Earthquake cluster along San Andreas Fault M7.3 43 aftershocks in 18.2days All-Cal model – SCEC Simulator Comparison Project

18. 186/9/2011UCERF3 / EQ Simulators Workshop Earthquake cluster along San Andreas Fault M6.9 Followed by 6 aftershocks in 4.8 minutes All-Cal model – SCEC Simulator Comparison Project

19. 196/9/2011UCERF3 / EQ Simulators Workshop Earthquake cluster along San Andreas Fault M7.2 All-Cal model – SCEC Simulator Comparison Project

20. 206/9/2011UCERF3 / EQ Simulators Workshop 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 Colella et al., submitted Colella et al., submitted Slow-slip events

21. 216/9/2011UCERF3 / EQ Simulators Workshop Summary or Conclusions (if appropriate or desired)