Earthquake potential of the San Andreas and North Anatolian Fault Zones: A comparative look

1. Earthquake potential of the San Andreas and North Anatolian Fault Zones:A comparative look M. B. Sørensen Department of Earth Science, University of Bergen, Norway, Department of Earth Science

2. B. Bryant A. Barka SCEC A. Barka Department of Earth Science University of Bergen Earthquake potential • The likelihood of a given fault or fault zone to generate an earthquake at a given time • Controls largely the seismic hazard in a region • Controlled by factors such as maximum expected magnitudes, recurrence times, time elapsed since last large earthquake, stress transfer from other earthquakes and fault vs. rupture segmentation

3. Department of Earth Science University of Bergen Global earthquake distribution Institutt for geovitenskap / Bergen Museum

4. Department of Earth Science University of Bergen SAFZ and NAFZ N. Toksoz USGS, 2000

5. Department of Earth Science University of Bergen SAFZ and NAFZ

6. B. Bryant A. Barka SCEC A. Barka Department of Earth Science University of Bergen This presentation • San Andreas Fault Zone • North Anatolian Fault Zone • Comparison of earthquake potential • - maximum expected mangitude • - earthquake recurrence • - historical earthquakes • - coulomb stress • - rupture segmentation • Implications for seismic hazard • Conclusions

7. Department of Earth Science University of Bergen San Andreas Fault Zone Photo: R. Wallace

8. Department of Earth Science University of Bergen San Andreas Fault Zone Wallace, 1990

9. Department of Earth Science University of Bergen San Andreas Fault Zone - evolution Irwin, 1990 Animation

10. Department of Earth Science University of Bergen San Andreas Fault Zone - segmentation Wallace, 1990 Four main segments: a) 1906 rupture and subparallel branches b) Central California active (creeping) section c) 1857 rupture d) Southern section (south of Transverse ranges) Additional faults are important parts of the system

11. Department of Earth Science University of Bergen San Andreas Fault Zone - geomorphology Wallace, 1990

12. R. Wallace R. Wallace USGS/SCAMP USGS M. Rymer NASA Department of Earth Science University of Bergen San Andreas Fault Zone - geomorphology

13. Department of Earth Science University of Bergen San Andreas Fault – major earthquakes SCEC, 2006

14. Department of Earth Science University of Bergen San Andreas Fault Zone – creeping section Schulz and Wallace, 1997

15. Department of Earth Science University of Bergen North Anatolian Fault Zone Photo: S. Pucci

16. Department of Earth Science University of Bergen North Anatolian Fault Zone Armijo et al., 2005

17. Department of Earth Science University of Bergen North Anatolian Fault Zone - evolution • 11-13 My ago: Arabia/Eurasia collision  Anatolia moves west  creation of NAF in eastern Turkey • NAF propagates westwards (~11 cm/yr) • Marmara Sea segment is ~200 000 years old Armijo et al., 2005

18. Department of Earth Science University of Bergen North Anatolian Fault Zone - segmentation Barka and Kadinsky-Cade, 1988

19. Department of Earth Science University of Bergen North Anatolian Fault Zone - geomorphology Sengor et al., 2005

20. U. Arizona Aksoy, 2004 Pucci, 2005 Aksoy, 2004 U. Arizona Department of Earth Science University of Bergen North Anatolian Fault Zone - geomorphology

21. Department of Earth Science University of Bergen North Anatolian Fault Zone – major earthquakes Barka et. al. (2002)

22. Department of Earth Science University of Bergen Factors affecting earthquake potential

23. B. Bryant A. Barka SCEC A. Barka Department of Earth Science University of Bergen Factors affecting earthquake potential • Maximum expected magnitude • Earthquake recurrence • Time elapsed since last large earthquake • Coulomb stress transfer • Fault segmentation

24. Department of Earth Science University of Bergen Maximum expected magnitude • One factor controlling earthquake magnitude is rupture area • Empirical study by Wells and Coppersmith (1994) gives relation between rupture length and magnitude • For strike-slip faults:

25. Department of Earth Science University of Bergen Maximum expected magnitude - SAFZ • Precence of creeping sections limits the maximum magnitude along SAF • Maximum expected magnitude M=8+ Schulz and Wallace, 1997

26. Barka et. al. (2002) Department of Earth Science University of Bergen Maximum expected magnitude - NAFZ • Controlled by fault segmentation • Limited by significant fault bends or offsets • Maximum expected magnitude M=8.0

27. 1906 1857 ?? Department of Earth Science University of Bergen Earthquake recurrence • San Andreas: M8 every several hundres years in N and S sections (e.g. 1857,1906) • Also smaller events at these locked sections (e.g. 1989 Loma Prieta, M=7.1) • M6 along the entire fault (e.g. Parkfield), larger events are rare at creeping sections • Reflected in microseismicity • For entire SAF: M6 every 15 months, M7 every 12.5 years, M8 every 125 years (Ellsworth, 1990 based on 220 years earthquake catalogue) Modified from Hill et al., 1990

28. Department of Earth Science University of Bergen Earthquake recurrence • North Anatolian: M=7+ events rupture all segments along the fault with intervals of 450 ± 220 years • Creeping section near Ismetpasa (1 cm/yr) within 1944 rupture area • M=6 every 2-4 years, M=7 every ~10 years quiescence before 1939  sequence Toksoz et al., 1979 Complete for M>5.5

29. Department of Earth Science University of Bergen Earthquake magnitude and recurrence

30. Department of Earth Science University of Bergen Time elapsed since last earthquake Recent major earthquakes in California Smith and Sandwell, 2006

31. Department of Earth Science University of Bergen Time elapsed since last earthquake Recent major earthquakes along the North Anatolian Fault Barka et. al. (2002)

32. Department of Earth Science University of Bergen Coulomb stress change • Effect of an earthquake on the surrounding faults due to transfer of stresses • Typical level of stress change is a few bars (few percent of typical earthquake stress drop) • Such a change affects the time required for tectonic stressing to bring a segment to faliure • Can be implemented in hazard assessment by converting the change into a change in the probability of a future earthquake Stein and Lisowski

33. Department of Earth Science University of Bergen Stress transfer – San Andreas Fault Zone Southern california example: the area of the M=7.3 1992 Landers earthquake Several large earthquakes occurred here during 1975-1999 Short distance between neighboring faults gives complicated stress transfer effects Red: increased stress, blue: decreased stress, gray dots: aftershocks Toda et al., 2005 Animation

34. Department of Earth Science University of Bergen Stress transfer – North Anatolian Fault Zone Westward migration of large earthquakes Stein et al., 1996 Animation

35. Department of Earth Science University of Bergen Stress transfer – North Anatolian Fault Zone Earthquake history of the North Anatolian Fault Stein et al., 1996 Animation

36. Department of Earth Science University of Bergen Coulomb stress change

37. Department of Earth Science University of Bergen Fault segmentation - SAFZ • Major earthquakes rupture entire fault sections limited by creeping central segment • Smaller events occur along these segments at locations with low slip during major event • Highly regular earthquake occurrence is observed at some places, e.g. Parkfield • High number of parallel faults can rupture in individual events Smith and Sandwell, 2006

38. Department of Earth Science University of Bergen Fault segmentation - NAFZ Barka and Kadinsky-Cade, 1988

39. Department of Earth Science University of Bergen Fault segmentation - NAFZ • Major earthquakes occur repeatedly but rupture segmentation is not repeated • Westward migration of earthquakes does not seem to be a general trend Meghraoui, 2004 Stein et al., 1996

40. Department of Earth Science University of Bergen Fault segmentation

41. Department of Earth Science University of Bergen Seismic hazard – short term • San Andreas Fault Zone • San Francisco bay area • Southern California • North Anatolian Fault Zone • Istanbul • East of Erzincan Sengor et al., 2005 WGCEP, 1988

42. USGS, 2003 Department of Earth Science University of Bergen Seismic hazard – San Fransisco

43. Department of Earth Science University of Bergen Seismic hazard – Southern California • Many faults affect the hazard in the region • Densely populated part of California including Los Angeles • Hidden (unknown) faults are present – for example 1994 M=6.7 Northridge earthquake SCEC, 2006

44. (Pulido et al., 2004) Department of Earth Science University of Bergen Seismic hazard – Istanbul • 35-70% probability of a M=7+ earthquake in the Marmara Sea within the next 30 years (Parsons, 2004) • Scenario based ground motion modelling estimates ground shaking level

45. Department of Earth Science University of Bergen Seismic hazard – Eastern Turkey • Last rupture in 1784 • Confined by 1992 and 1949 ruptures (potential M=7+ earthquake) • 1992 earthquake (M~6.7) caused significant damage in Erzincan Stein et al., 1996 Photos: M. Yoshimine

46. Department of Earth Science University of Bergen Seismic hazard – short term USGS, 2006 Atakan and Sørensen, 2006

47. Department of Earth Science University of Bergen Seismic hazard – long term California Turkey Erdik et al., 1999 Petersen et al., 2003

48. Department of Earth Science University of Bergen Conclusions

49. Department of Earth Science University of Bergen

50. Department of Earth Science University of Bergen