1. Epistemic uncertainty in California-wide simulations of synthetic seismicity Fred Pollitz, USGS Menlo Park Acknowledgments: David Schwartz, Steve Ward

3. Ward (2000)

4. Rundle et al. (2008)

5. Capabilities of this simulator

6. Inherently discrete fault zone Inherently discrete fault zone (Ben-Zion and Rice model) (Ben-Zion and Rice model) Homogeneous, planar faults Homogeneous, planar faults Viscoelasticity of lower crust/upper mantle Viscoelasticity of lower crust/upper mantle --> loading through backslip in the --> loading through backslip in the fully relaxed limit fully relaxed limit

7. Fault network and slip rates courtesy of Steve Ward (June, 2009) Original set of ~4 x 3 km 2 patches are re-grouped and subdivided into set of smoothly-connected, non-overlapping ~1 x 1 km 2 patches 101208 fault patches

16. Stress history on a single fault patch Static frictional stress Dynamic frictional stress Arrest stress Dynamic overshoot parameter: Stress reduction parameter:  =  s -  a D =  s -  a )/(  s -  d )

19. Simulator parameters Dynamic overshoot parameter: Stress reduction parameter:  =  s -  a D =  s -  a )/(  s -  d ) Shape of slip-weakening curve Mantle viscosity  m

20. Twenty consecutive M>6.7 ruptures M6.9

21. M7.2

22. M7.0

23. M7.6

24. M6.7

25. M7.5

26. M7.6

27. M7.2

28. M6.7

30. M7.7

31. M7.3

32. M7.5

33. M7.3

35. M7.2

36. M6.7

37. M7.2

38. M7.3

39. M7.5

40. mean recurrence interval (for given magnitude threshold) magnitude-frequency statistics, e.g. b-value coefficient of variation conditional rupture probability Simulator results

41. Hanks and Bakun (2007 )

44. Magnitude-frequency statistics

45. magnitude log 10 [earthquake production rate (yr -1 )] With slip weakening D=1.25  m = 1.2 x 10 19 Pa s

46. With slip weakening D=1.25  m = 1.2 x 10 19 Pa s

48. Low Mantle Viscosity

49. High Mantle Viscosity

52. magnitude log 10 [earthquake production rate (yr -1 )]

55. Fault system behavior is sensitive to simple parameters Simulations capture Gutenberg-Richter and characteristic-earthquake behavior Comparison of slip maps for the southern SAF suggests that the ‘slip barrier’ nature of a segment boundary depends substantially on mantle viscosity Characteristic magnitude and mean recurrence interval may exhibit a systematic dependence on mantle viscosity Conclusions