The power of intuition (Selwyn’s that is). Selwyn’s career goal #__: What does the asthenosphere...
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- The power of intuition (Selwyns that is)
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- Selwyns career goal #__: What does the asthenosphere have to do
with earthquakes, crustal motions, and mantle convection?
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- Upper crust Lower crust Upper mantle Upper crust Lower crust
Upper mantle Figures courtesy of Liz Hearn
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- Time (years) Elastic crust Viscoelastic asthenosphere
Viscoelastic upper mantle Steve Cohen Cohen (1992) Far field Near
field Horizontal Stress
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- Physics says that the lower crust and upper mantle have to
relax the coseismic stresses imparted by an earthquake
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- 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... Earthquake-pattern inference of
rheology Rydelek and Sacks (1990) Paul Rydelek
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- Rydelek and Sacks (1990) 7.5-7.9 6.5-6.9 Magnitude 7.0-7.4
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- Rydelek and Sacks (1990)
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- Post-earthquake mantle relaxation (1896 Riku-U eq.) Rydelek and
Sacks (1990)
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- Paradigm shift in Earths 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
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- 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.
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- Asthenosphere relaxation must lead to long-range transfer of
crustal stress from one fault to another
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- Reduced friction 1995 earthquake triggering
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- 1944/1646 to 1995 postseismic stress change bars
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- Pollitz and Sacks (1997)Heinze and Sacks (1979)
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- Geodetic inference of rheology
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- 1999 M7.1 Hector Mine earthquake
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- Freed and Burgmann (2004) Post-earthquake (M7.1 1999 Hector
Mine eq.) Andy Freed (Purdue Univ.)
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- Post-earthquake (M7.5 1959 Hebgen Lake, Idaho, earthquake)
Nishimura and Thatcher (2003)
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- Post-lake-filling (1935: Lake Mead, Nevada) Kaufmann and
Amelung (2000) 200 mm subsidence from 1935-1950
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- Gourmelen and Amelung (2005) Post-earthquake (1915-1954;
Central Nevada Seismic Zone)
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- Post-earthquake (1915-1954; Central Nevada Seismic Zone)
Elastic thickness (km)Lower crust viscosity (Pa s) Underlying layer
viscosity (Pa s) Gourmelen and Amelung (2005)
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- Geologic inference of rheology
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- Figures courtesy of Bruce Bills
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- Post-lacustrine unloading (Paleolake Lahontan, Nevada)
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- 2m 4m Adams et al. (1999), Bills et al. (2007) Up to 15m uplift
since 15 kyrBP
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- Bills et al. (2007) Post-lacustrine unloading (Paleolake
Lahontan, Nevada) High-viscosity crust Low-viscosity mantle
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- Bills et al. (1994) Post-lacustrine unloading (Paleolake
Bonneville, Utah)
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- James et al. (2000) Post-glacial rebound
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- Modified from Dixon et al. (2004) Jacqueline DixonTim
Dixon
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- Goes and van der Lee (2002)
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- Paradigm shift in Earths 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
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- Rheology of the Lower Crust and Upper Mantle: Evidence from
Rock Mechanics, Geodesy and Field Observations, Annu. Rev. Earth
Planet. Sci. (2008) Roland BurgmannGeorg Dresen
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- American Geophysical Union 2010 Fall Meeting Linking Geodetic
Observations to Mechanical Properties of the Lithosphere: New
Methods and Models I, II Wayne ThatcherLiz HearnEric HetlandSylvain
BarbotYuri Fialko
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- SCEC Workshop on Ductile Rheology of the Southern California
Lithosphere (May 1-2, 2013) Wayne ThatcherLiz HearnGreg Hirth
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