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The power of intuition (Selwyn’s that is)

The power of intuition (Selwyn’s that is). Selwyn’s career goal #__: What does the asthenosphere have to do with earthquakes, crustal motions, and mantle convection?. Upper crust. Upper crust. Lower crust. Lower crust. Upper mantle. Upper mantle. Figures courtesy of Liz Hearn.

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The power of intuition (Selwyn’s that is)

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  1. The power of intuition (Selwyn’s that is)

  2. Selwyn’s career goal #__: What does the asthenosphere have to do with earthquakes, crustal motions, and mantle convection?

  3. Upper crust Upper crust Lower crust Lower crust Upper mantle Upper mantle Figures courtesy of Liz Hearn

  4. Figures courtesy of Liz Hearn

  5. crust mantle (asthenosphere)

  6. crust mantle (asthenosphere)

  7. crust mantle (asthenosphere)

  8. crust mantle (asthenosphere)

  9. crust mantle (asthenosphere)

  10. Horizontal Stress Elastic crust Far field Viscoelasticasthenosphere Viscoelastic upper mantle Near field Time (years) Cohen (1992) Steve Cohen

  11. “Physics says that the lower crust and upper mantle have to relax the coseismic stresses imparted by an earthquake”

  12. Earthquake-pattern inference of rheology “A significant correlation is found, in both space and time, between the intraplate (land) and interplate (sea, thrust zone only) earthquakes in Tohoku, NE Japan that has persisted since the times of reliably reported events in AD 1600. The correlation peaks at a land-lead of about 36 yr...” Rydelek and Sacks (1990) Paul Rydelek

  13. 7.5-7.9 7.0-7.4 6.5-6.9 Magnitude 6.5-6.9 7.0-7.4 7.5-7.9 Rydelek and Sacks (1990)

  14. Rydelek and Sacks (1990)

  15. Post-earthquake mantle relaxation (1896 Riku-U eq.) Rydelek and Sacks (1990)

  16. Paradigm shift in Earth’s continental tectonics, from Time-independent crustal deformation, punctuated only by crustal earthquakes and associated localized brittle/plastic deformation, to… Time-dependent crustal deformation, involving deep-seated, ductile flow and associated broadscale deformation

  17. Pollitz, F. F., and I. S. Sacks, Modeling of postseismic relaxation following the Great 1857 Earthquake, southern California, Bull. Seismol. Soc. Am., 82, 454-480, 1992. Pollitz, F. F., and I. S. Sacks, Fault model of the 1891 Nobi earthquake from historic triangulation and leveling, J. Phys. Earth, 42, 1-43, 1994. Pollitz, F. F., and I. S. Sacks, Consequences of stress changes following the 1891 Nobi earthquake, Japan, Bull. Seismol. Soc. Am., 85, 796-807, 1995. Pollitz, F. F., and I. S. Sacks, Viscosity structure beneath northeast Iceland, J. Geophys. Res, 101, 17,771-17,793, 1996. Pollitz, F. F., and I. S. Sacks, The 1995 Kobe, Japan earthquake: A long-delayed aftershock of the offshore 1944 Tonankai and 1946 Nankaido earthquakes, Bull. Seismol. Soc. Am., 87, 1- 10, 1997. Pollitz, F. F., and I. S. Sacks, Stress triggering of the 1999 Hector Mine earthquake by transient deformation following the 1992 Landers earthquake, Bull. Seismol. Soc. Am. 92, 1487-1496, 2002.

  18. “Asthenosphere relaxation must lead to long-range transfer of crustal stress from one fault to another”

  19. M6.8 Kobe earthquake

  20. Reduced friction  1995 earthquake triggering

  21. 1944/1646 to 1995 postseismic stress change bars

  22. Pollitz and Sacks (1997) Heinze and Sacks (1979)

  23. Geodetic inference of rheology

  24. 1999 M7.1 Hector Mine earthquake

  25. Post-earthquake (M7.1 1999 Hector Mine eq.) Freed and Burgmann (2004) Andy Freed (Purdue Univ.)

  26. Post-earthquake (M7.5 1959 HebgenLake, Idaho, earthquake) Nishimura and Thatcher (2003)

  27. Post-lake-filling (1935: Lake Mead, Nevada) 200 mm subsidence from 1935-1950 Kaufmann and Amelung(2000)

  28. Post-earthquake (1915-1954; Central Nevada Seismic Zone) Gourmelenand Amelung(2005)

  29. Post-earthquake (1915-1954; Central Nevada Seismic Zone) Gourmelenand Amelung(2005) Underlying layer viscosity (Pa s) Elastic thickness (km) Lower crust viscosity (Pa s)

  30. Geologic inference of rheology

  31. Figures courtesy of Bruce Bills

  32. Post-lacustrine unloading (Paleolake Lahontan, Nevada)

  33. Post-lacustrine unloading (Paleolake Lahontan, Nevada) Up to 15m uplift since 15 kyrBP 4m 2m Adams et al. (1999), Bills et al. (2007)

  34. Post-lacustrine unloading (Paleolake Lahontan, Nevada) High-viscosity crust Low-viscosity mantle Bills et al. (2007)

  35. Post-lacustrine unloading (Paleolake Bonneville, Utah) Bills et al. (1994)

  36. Post-glacial rebound James et al. (2000)

  37. Modified from Dixon et al. (2004) Jacqueline Dixon Tim Dixon

  38. Goes and van der Lee (2002)

  39. Paradigm shift in Earth’s continental tectonics, from Time-independent crustal deformation, punctuated only by crustal earthquakes and associated localized brittle/plastic deformation, to… Time-dependent crustal deformation, involving deep-seated, ductile flow and associated broadscale deformation

  40. “Rheology of the Lower Crust and Upper Mantle: Evidence from Rock Mechanics, Geodesy and Field Observations”, Annu. Rev. Earth Planet. Sci. (2008) Georg Dresen Roland Burgmann

  41. American Geophysical Union 2010 Fall Meeting Linking Geodetic Observations to Mechanical Properties of the Lithosphere: New Methods and Models I, II Wayne Thatcher Liz Hearn Eric Hetland Sylvain Barbot Yuri Fialko

  42. SCEC Workshop on Ductile Rheology of the Southern California Lithosphere (May 1-2, 2013) Wayne Thatcher Liz Hearn Greg Hirth

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