InSAR observations of lake loading at Yangzhuoyong Lake, Tibet: Constraints on crustal elasticity

- InSAR time-series detects up to 2.5 mm radar LOS displacement for 1 m lake level drop.
- Layered elastic model indicates a Young's modulus of 50±9GPa at the top 15 km of crust.
- The modeled static Young's modulus is ∼25% smaller than the seismic derived dynamic one.

We use Envisat 2003-2010 InSAR imagery over Yangzhuoyong Lake in southeastern Tibet to study the elastic response of the Earth's crust to variations in lake level. The net lake level drop during our study period is ∼3 m with seasonal variations of more than 1 m. The time-series close to the lake center shows a high correlation with the lake level history. Near the lake center the unit response with respect to lake level change is 2.5 mm/m in radar line-of-sight direction, or ∼2.7 mm/yr in vertical direction, corresponding to a vertical response of ∼4.3 mm/Gt load change. We show that the observations are most sensitive to the elastic properties of the crust in the 5-15 km depth range and explain them with a layered elastic half-space model with a Young's modulus of 50±9GPa Young's modulus in the top 15 km of the crust and using moduli inferred from seismology at greater depth. The inferred Young's modulus is ∼25% smaller than the seismic modulus, which we attribute to damaged rock and the presence of fluids.