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ICESat Derived Lithospheric Flexure as Caused by an Endorheic Lake’s Expansion on the Tibetan Plateau and its Rheological Constraints

  • Author(s): Madson, Austin
  • Advisor(s): Sheng, Yongwei
  • et al.
Abstract

A substantial and rapid expansion beginning in the late 1990s of Siling Co, the largest endorheic lake on the central Tibetan Plateau (TP), has caused a measurable deflection in the region adjacent to the lake. Current broad-scale measuring of this flexural response is mainly derived from DInSAR processing techniques. The underlying lithospheric response to large lake loads in this region is not well understood, with the focus on either a viscoelastic or an elastic response. This thesis intends to use a more efficient LiDAR remote sensing technique to measure the deflection in the vicinity of Siling Co, and to investigate the mechanisms of the observed lithospheric response. A lake-adjacent deflection rate and Siling Co water load variations are calculated utilizing the Geoscience Laser Altimeter System (GLAS) onboard NASA’s Ice, Cloud and land Elevation Satellite (ICESat) and the joint NASA/USGS Landsat series of earth observing satellites. A downward deflection rate of ~5.6 mm/yr for the first 4 km of lake-adjacent land is determined from the GLAS instrument and this response is compared to the flexural outputs from a spherically symmetric, non-rotating, elastic, and isotropic (SNREI) Earth model in order to better understand the underlying mechanisms of the lithospheric response to the extreme change in Siling Co loads. The modeled elastic response is ~6.7 times lower than the GLAS derived flexure, thereby providing further evidence that a completely elastic lithospheric response cannot explain the deflection in this region, and that a viscoelastic response is more likely. The relationship between the modeled elastic response and the GLAS derived flexure is applied to a long-term lake load change dataset to create the longest-running flexural response curve as caused by the last ~40 years of Siling Co load variations.

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