Jurnal Internasional The Cathles parameter (Ct): Definisi geodinamik dari astenosfer dan implikasi untuk sifat lempeng tektonik – Richards – – Geokimia, Geofisika, Geosystems
A weak asthenosphere, or low viscosity zone (LVZ) underlying the Earth's lithosphere has played an important role in interpreting isostasy, post-glacial rebound (PGR), and seismic low speed zones, as well as the proposed mechanism for continental drift, plate tectonics, and post-seismic relaxation (PSR). Consideration of the strength of completion of PGR, PSR, and geoid modeling studies showing sublithospheric LVZ may be ~ 100-200 km thick with ~ 100-1000 viscosity contrast.  Ab initio [numeric] a numerical model of boundary layer motion such as a plate in mantle convection also shows a key role for LVZ. Paradoxically, thinner LVZ with strong viscosity contrast is most effective in promoting surface movements such as plates. This numerical result is explained in terms of reducing horizontal shear dissipation due to LVZ, and simple scale theory leads to model predictions that are rather not intuitive. For example, LVZ causes an enlargement of stress at the base of the lithosphere, increasing plate boundary formation. Also, flow in LVZ can be driven by a plate (Couette flow), or pressure-driven from within the mantle (Poiseuille stream), depending on the extent to which the plate locally inhibits or drives the underlying mantle convection. For studies of wavelength geoid, PGR, and mantle convection, simple dimensionless parameters control the LVZ effect. This “parameter catheter” is given by Ct. = η * ( D / λ ) 3 where η * is the viscosity contrast and D is the LVZ thickness, and λ is the flow wavelength, emphasizing the tight-coupling tradeoff between LVZ thickness and viscosity contrast.