Oral PHD thesis defense by Yunguo Chen

On October 20th, Mr. Yunguo Chen defensed his PH.D thesis "青藏高原震后动力学过程及其壳幔流变属性研究" . In his thesis, Yunguo studied three main postseismic processes, that is, the poroelastic rebound (PE), afterslip of the fault, and viscoelastic relaxation in the lower crust and upper mantle of the 2008 Wenchuan earthquake, 2001 Kunlun earthquake, 1997 Manyi earthquake, 2010 Yushu and 2021 Maduo earthquakes. He constructed viscoelastic three-dimensional finite-element models (FEM) of each large earthquake based the coseismic rupture, the layered structure of the lithosphere, and rock physical properties. He constrained the regional rheological structure of the lower crust and upper mantle in Tibet using GNSS and InSAR observations. Model results indicate that the afterslip of the fault mainly controls the early-stage postseismic deformation in the near field, while the viscoelastic relaxation in the lower crust and upper mantle mainly controls the postseismic deformation in the middle- and far field. The PE together with the heterogeneity of rock physical property and other deformation processes may be secondary-order processes and be responsible for higher-order surface deformation. The research results have important significance on understanding the formation and evolution of the Tibetan Plateau.