Lithospheric thickness from surface waves

1
Lithospheric thickness (from surface waves)
Turcotte Schubert 2002
2
Elastic thickness
EQ depth
Shear wave velocity
Stein Wysession, 1993
50 100 150
3
Ocean floor bathymetry
Turcotte Schubert 2002
4
Heat flow
Turcotte Schubert 2002
5
Half space cooling model Problem with old
lithosphere

• Bathymetry and heat flow higher than predicted
• Additional source of heat for older lithosphere?
• E.g., small scale convection
• Models with better fit
• Plate model (Parson Sclater, JGR, 82, 803,
  1997)
• GDH1 (Stein and Stein, Nature, 359, 123, 1992)
• Provide additional heat through fixed plate
  thickness
• Better model fit
• Physical mechanism unclear

6
20 Myr
30 Myr
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Physical mechanisms - small scale convection -
temporal variability (e.g., Cretaceous hot
period) - random rejuvenation (hotspots,
seamounts).
Improved bathymetry from satellite and shipboard
tracks (Smith and Sandwell, Science, 1997)