Earthquake potential of the San Andreas
and North Anatolian Fault Zones:
A comparative look
M. B. Sørensen
Department of E...
SCEC A. Barka
B. Bryant A. Barka
Department of Earth Science
University of Bergen
Earthquake potential
• The likelihood of...
Department of Earth Science
University of Bergen
Global earthquake distribution
Institutt for geovitenskap / Bergen Museum
Department of Earth Science
University of Bergen
SAFZ and NAFZ
USGS, 2000
N. Toksoz
Department of Earth Science
University of Bergen
SAFZ and NAFZ
SCEC A. Barka
B. Bryant A. Barka
Department of Earth Science
University of Bergen
This presentation
• San Andreas Fault Zo...
Department of Earth Science
University of Bergen
San Andreas Fault Zone
Photo: R. Wallace
Department of Earth Science
University of Bergen
San Andreas Fault Zone
Wallace, 1990
Department of Earth Science
University of Bergen
San Andreas Fault Zone - evolution
Animation
Irwin, 1990
Department of Earth Science
University of Bergen
San Andreas Fault Zone - segmentation
Wallace, 1990
Four main segments:
a...
Department of Earth Science
University of Bergen
San Andreas Fault Zone - geomorphology
Wallace, 1990
Department of Earth Science
University of Bergen
San Andreas Fault Zone - geomorphology
R. Wallace
R. Wallace M. Rymer
NAS...
Department of Earth Science
University of Bergen
San Andreas Fault – major earthquakes
SCEC, 2006
Department of Earth Science
University of Bergen
San Andreas Fault Zone – creeping section
Schulz and Wallace, 1997
Department of Earth Science
University of Bergen
North Anatolian Fault Zone
Photo: S. Pucci
Department of Earth Science
University of Bergen
North Anatolian Fault Zone
Armijo et al., 2005
Department of Earth Science
University of Bergen
North Anatolian Fault Zone - evolution
• 11-13 My ago: Arabia/Eurasia col...
Department of Earth Science
University of Bergen
North Anatolian Fault Zone - segmentation
Barka and Kadinsky-Cade, 1988
Department of Earth Science
University of Bergen
North Anatolian Fault Zone - geomorphology
Sengor et al., 2005
Department of Earth Science
University of Bergen
North Anatolian Fault Zone - geomorphology
Aksoy, 2004
Aksoy, 2004
Pucci,...
Department of Earth Science
University of Bergen
North Anatolian Fault Zone – major earthquakes
Barka et. al. (2002)
Department of Earth Science
University of Bergen
Factors affecting earthquake potential
SCEC A. Barka
B. Bryant A. Barka
Department of Earth Science
University of Bergen
Factors affecting earthquake potential
•...
Department of Earth Science
University of Bergen
Maximum expected magnitude
• One factor controlling earthquake magnitude ...
Department of Earth Science
University of Bergen
Maximum expected magnitude - SAFZ
Schulz and Wallace, 1997
• Precence of ...
Department of Earth Science
University of Bergen
Maximum expected magnitude - NAFZ
Barka et. al. (2002)
• Controlled by fa...
Department of Earth Science
University of Bergen
Earthquake recurrence
• San Andreas: M≈8 every several hundres years in N...
Department of Earth Science
University of Bergen
Earthquake recurrence
• North Anatolian: M=7+ events rupture all segments...
Department of Earth Science
University of Bergen
Earthquake magnitude and recurrence
SAFZ NAFZ
Creeping segment in central...
Department of Earth Science
University of Bergen
Time elapsed since last earthquake
Recent major earthquakes in California...
Department of Earth Science
University of Bergen
Time elapsed since last earthquake
Recent major earthquakes along the Nor...
Department of Earth Science
University of Bergen
Coulomb stress change
•Effect of an earthquake on the
surrounding faults ...
Department of Earth Science
University of Bergen
Stress transfer – San Andreas Fault Zone
Southern california example: the...
Department of Earth Science
University of Bergen
Stress transfer – North Anatolian Fault Zone
Westward migration of large ...
Department of Earth Science
University of Bergen
Stress transfer – North Anatolian Fault Zone
Earthquake history of the No...
Department of Earth Science
University of Bergen
Coulomb stress change
SAFZ NAFZ
Coulomb stress transfer results are
compl...
Department of Earth Science
University of Bergen
Fault segmentation - SAFZ
• Major earthquakes rupture entire fault
sectio...
Department of Earth Science
University of Bergen
Fault segmentation - NAFZ
Barka and Kadinsky-Cade,
1988
Meghraoui, 2004
Department of Earth Science
University of Bergen
Fault segmentation - NAFZ
• Major earthquakes occur repea...
Department of Earth Science
University of Bergen
Fault segmentation
SAFZ NAFZ
The SAF is more smooth
and generally rupture...
Department of Earth Science
University of Bergen
Seismic hazard – short term
San Andreas Fault Zone
• San Francisco bay ar...
Department of Earth Science
University of Bergen
Seismic hazard – San Fransisco
USGS, 2003
Department of Earth Science
University of Bergen
Seismic hazard – Southern California
• Many faults affect the hazard in t...
Department of Earth Science
University of Bergen
Seismic hazard – Istanbul
(Pulido et al., 2004)
• 35-70% probability of a...
Department of Earth Science
University of Bergen
Seismic hazard – Eastern Turkey
• Last rupture in 1784
• Confined by 1992...
Department of Earth Science
University of Bergen
Seismic hazard – short term
SAFZ NAFZ
Both fault zones are characterized ...
Department of Earth Science
University of Bergen
Seismic hazard – long term
California
Turkey
Petersen et al., 2003
Erdik ...
Department of Earth Science
University of Bergen
Conclusions
SAFZ NAFZ
Two major fault systems with similar length, direct...
Department of Earth Science
University of Bergen
Department of Earth Science
University of Bergen
Department of Earth Science
University of Bergen
Earthquake recurrence
Time vs. distance plot of known
damaging earthquake...
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Comparison Between San Andreas Fault and North Anatolian Fault

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Comparison Between San Andreas Fault and North Anatolian Fault

  1. 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. 2. SCEC A. Barka B. Bryant 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. 3. Department of Earth Science University of Bergen Global earthquake distribution Institutt for geovitenskap / Bergen Museum
  4. 4. Department of Earth Science University of Bergen SAFZ and NAFZ USGS, 2000 N. Toksoz
  5. 5. Department of Earth Science University of Bergen SAFZ and NAFZ
  6. 6. SCEC A. Barka B. Bryant 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. 7. Department of Earth Science University of Bergen San Andreas Fault Zone Photo: R. Wallace
  8. 8. Department of Earth Science University of Bergen San Andreas Fault Zone Wallace, 1990
  9. 9. Department of Earth Science University of Bergen San Andreas Fault Zone - evolution Animation Irwin, 1990
  10. 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. 11. Department of Earth Science University of Bergen San Andreas Fault Zone - geomorphology Wallace, 1990
  12. 12. Department of Earth Science University of Bergen San Andreas Fault Zone - geomorphology R. Wallace R. Wallace M. Rymer NASA USGS USGS/SCAMP
  13. 13. Department of Earth Science University of Bergen San Andreas Fault – major earthquakes SCEC, 2006
  14. 14. Department of Earth Science University of Bergen San Andreas Fault Zone – creeping section Schulz and Wallace, 1997
  15. 15. Department of Earth Science University of Bergen North Anatolian Fault Zone Photo: S. Pucci
  16. 16. Department of Earth Science University of Bergen North Anatolian Fault Zone Armijo et al., 2005
  17. 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. 18. Department of Earth Science University of Bergen North Anatolian Fault Zone - segmentation Barka and Kadinsky-Cade, 1988
  19. 19. Department of Earth Science University of Bergen North Anatolian Fault Zone - geomorphology Sengor et al., 2005
  20. 20. Department of Earth Science University of Bergen North Anatolian Fault Zone - geomorphology Aksoy, 2004 Aksoy, 2004 Pucci, 2005 U. Arizona U. Arizona
  21. 21. Department of Earth Science University of Bergen North Anatolian Fault Zone – major earthquakes Barka et. al. (2002)
  22. 22. Department of Earth Science University of Bergen Factors affecting earthquake potential
  23. 23. SCEC A. Barka B. Bryant 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. 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: Magnitude Rupture length 6 14 km 7 60 km 7.5 120 km 8 245 km
  25. 25. Department of Earth Science University of Bergen Maximum expected magnitude - SAFZ Schulz and Wallace, 1997 • Precence of creeping sections limits the maximum magnitude along SAF • Maximum expected magnitude M=8+
  26. 26. Department of Earth Science University of Bergen Maximum expected magnitude - NAFZ Barka et. al. (2002) • Controlled by fault segmentation • Limited by significant fault bends or offsets • Maximum expected magnitude M=8.0
  27. 27. 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) 1906 1857 ?? Modified from Hill et al., 1990
  28. 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 Complete for M>5.5 Toksoz et al., 1979
  29. 29. Department of Earth Science University of Bergen Earthquake magnitude and recurrence SAFZ NAFZ Creeping segment in central SAF limits the maximum magnitude to the levels observed for the 1857 and 1906 earthquakes (M~8) Largest known earthquake along NAF is 1668 (M~8), most known earthquakes are of smaller magnitude M=7+ every ~ 12.5 years M=7+ every ~ 10 years M~8 events occur regularly M~8 events are rare
  30. 30. Department of Earth Science University of Bergen Time elapsed since last earthquake Recent major earthquakes in California Smith and Sandwell, 2006
  31. 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. 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. 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 Animation Toda et al., 2005
  34. 34. Department of Earth Science University of Bergen Stress transfer – North Anatolian Fault Zone Westward migration of large earthquakes Animation Stein et al., 1996
  35. 35. Department of Earth Science University of Bergen Stress transfer – North Anatolian Fault Zone Earthquake history of the North Anatolian Fault Animation Stein et al., 1996
  36. 36. Department of Earth Science University of Bergen Coulomb stress change SAFZ NAFZ Coulomb stress transfer results are complex Coulomb stress transfer successful in describing potential locations of future earthquakes Simple, straight geometry → efficient stress transfer Short distance to other faults → irregular and complex stress transfer pattern Isolated from other faults → minimum transfer to competing faults Smooth trace → larger earthquakes En echelon geometry → keeps the entire fault from rupturing at once
  37. 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. 38. Department of Earth Science University of Bergen Fault segmentation - NAFZ Barka and Kadinsky-Cade, 1988
  39. 39. Meghraoui, 2004 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 Stein et al., 1996
  40. 40. Department of Earth Science University of Bergen Fault segmentation SAFZ NAFZ The SAF is more smooth and generally rupture in larger events but parallel faults take up part of the accumulated strain Many bends and offsets controls the rupture segmentation along NAFZ This results in large characteristic earthquakes along SAF and smaller events on neighbouring faults This generally results in smaller events than what is observed along SAF
  41. 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. 42. Department of Earth Science University of Bergen Seismic hazard – San Fransisco USGS, 2003
  43. 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. 44. Department of Earth Science University of Bergen Seismic hazard – Istanbul (Pulido et al., 2004) • 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. 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 Photos: M. Yoshimine Stein et al., 1996
  46. 46. Department of Earth Science University of Bergen Seismic hazard – short term SAFZ NAFZ Both fault zones are characterized by a significant seismic hazard towards a big city Risk mitigation efforts are important and should be prioritized (strengthening of buildings, information to the pubic, disaster planning etc.) earthquake forecasting IEEWRRS Atakan and Sørensen, 2006USGS, 2006
  47. 47. Department of Earth Science University of Bergen Seismic hazard – long term California Turkey Petersen et al., 2003 Erdik et al., 1999
  48. 48. Department of Earth Science University of Bergen Conclusions SAFZ NAFZ Two major fault systems with similar length, direction of motion, slip rate, age and straightness High seismic hazard in urban environments Maximum expected magnitude limited by creep Maximum expected magnitude limited by segmentation M=6+ every 15 months M=7+ every 12.5 years M=8+ every 125 years M=6+ every 2-4 years M=7+ every 10 years M=8+ rare Smooth trace implies large earthquakes Strong segmentation implies smaller events Many parallel faults cause a complicated stress transfer pattern Isolated fault gives little transfer of stresses to competing faults
  49. 49. Department of Earth Science University of Bergen
  50. 50. Department of Earth Science University of Bergen
  51. 51. Department of Earth Science University of Bergen Earthquake recurrence Time vs. distance plot of known damaging earthquakes along NAF for the time 400 BC to 2000 AD Tendency of lower activity level prior to 1500, may be due to incomplete historical records From Sengor et al., 2005
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