Details

Autor(en) / Beteiligte

• Yang, Ting
• Gurnis, Michael

Titel

Dynamic topography, gravity and the role of lateral viscosity variations from inversion of global mantle flow

Ist Teil von

• Geophysical journal international, 2016-11, Vol.207 (2), p.1186-1202

Ort / Verlag

Oxford University Press

Erscheinungsjahr

2016

Beschreibungen/Notizen

• Lateral viscosity variations (LVVs) in the mantle influence geodynamic processes and their surface expressions. With the observed long-wavelength geoid, free-air anomaly, gravity gradient in three directions and discrete, high-accuracy residual topography, we invert for depth- and temperature-dependent and tectonically regionalized mantle viscosity with a mantle flow model. The inversions suggest that long-wavelength gravitational and topographic signals are mainly controlled by the radial viscosity profile; the pre-Cambrian lithosphere viscosity is slightly (∼ one order of magnitude) higher than that of oceanic and Phanerozoic lithosphere; plate margins are substantially weaker than plate interiors; and viscosity has only a weak apparent, dependence on temperature, suggesting either a balancing between factors or a smoothing of actual higher amplitude, but short wavelength, LVVs. The predicted large-scale lithospheric stress regime (compression or extension) is consistent with the world stress map (thrust or normal faulting). Both recent compiled high-accuracy residual topography and the predicted dynamic topography yield ∼1 km amplitude long-wavelength dynamic topography, inconsistent with recent studies suggesting amplitudes of ∼100 to ∼500 m. Such studies use a constant, positive admittance (transfer function between topography and gravity), in contrast to the evidence which shows that the earth has a spatially and wavelength-dependent admittance, with large, negative admittances between ∼4000 and ∼104 km wavelengths.