Lower Crust Viscosity in Central Tibet Inferred From InSAR Derived Deformation Around Siling Co Lake After Its Rapid Expansion in the 2000s

Abstract

Constraining the lithospheric rheology of Tibetan Plateau is important for the physical understanding of its tectonics. Siling Co, the largest high-altitude lake in the world, has experienced a rapid water level increase in the 2000s. The resulting loading changes stimulate the viscoelastic response of the lower crust, giving access to study the lithospheric rheology in central Tibet. Here, we derive a clear subsidence signal around the lake with peak velocity of 4 mm/yr from two tracks of Sentinel-1 InSAR images acquired from 2017 to 2022. Our viscoelastic modeling suggests a ductile layer 15 km beneath the surface with a decadal-scale, steady-state viscosity of 1–4 × 1019 Pa s. This value is consistent with the viscosity inferred from millennium-scale shoreline changes, but is about 10 times higher than the viscosities derived from the deformation surrounding Siling Co before 2011, highlighting the role of transient viscosity in controlling the surface deformation.