Publication Date:
2015-06-13
Description:
The Siling Co lake is the largest endorheic lake in Central Tibet. Altimetric measures, combined with lake contours, show that in 1972-1999 its water level remained stable, while it increased by about 1.0 m/yr in the period 2000-2006. The increased rate gradually stepped down to 0.2 m/yr in 2007-2011. The ground motion associated with the water load increase is studied by InSAR using 107 ERS and Envisat SAR images during the period 1992-2011. The deformation amplitude closely follows the lake level temporal evolution, except that subsidence continues in 2008-2011, while the lake level stagnated. This temporal evolution suggests a non elastic relaxation process taking place at a decade time-scale. Phase delay maps are used to constrain possible layered visco-elastic rheological models. An elastic model could partly explain the observed subsidence rate if elastic moduli are about twice lower than those extracted from Vp/Vs profiles. The surface deformation pattern is also extracted by projecting the phase delay maps against the best-fit model temporal behavior. It shows that deep relaxation in the asthenosphere is negligible at the decade time-scale and favors the existence of a ductile channel in the deep crust above a more rigid mantle. Overall, the best fit model includes a ductile lower crust, with a viscosity of 1-3×10 18 Pa.s between 25-35 km and the Moho (at 65 km), overlying a rigid mantle.
Print ISSN:
0148-0227
Topics:
Geosciences
,
Physics
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