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Geodetic observation and modelling of fault deformation in the Tibetan Plateau

Abstract : Ongoing plate convergence between India and Eurasia during the past ∼40 million years has created the Tibetan Plateau, a region with average elevation of ~4500 m, area of over 600×1000 km2, and active faulting and crustal deformation extends more than 2000 km into central Asia. Approximately one-half of India’s 36–40 mm/a northward motion is partitioned in the Tibetan Plateau, resulting in crustal thickening, shortening, folds, and complex fault systems. The active crustal deformation cause diverse styles of strain accumulation and release on crustal faults, expressed as distinct faulting behavior or earthquake cycles. Investigating into crustal fault deformation and earthquake cycles in the Tibetan Plateau using space-based geodesy, i.e., Global Positioning System (GPS) and Synthetic Aperture Radar Interferometry (InSAR), has started 30 years ago. Currently, high spatial-temporal resolution geodesy provides us with abundant data and sufficient resolution to study the ground deformation associated with earthquake cycle processes.In this dissertation, I focus on the interseismic deformation along three boundary large strike-slip fault systems of the Tibetan Plateau, the Altyn Tagh fault, the Haiyuan fault system and the Xianshuihe-Anninghe-Zemuhe-Xiaojiang fault system (XAZX). I use GPS (1999-2018) and InSAR (2003-2016) geodetic observations, along with 2D dislocation and 3D block models, to invert for slip rates and interseismic fault coupling, assess seismic hazard and investigate earthquake cycles along these faults; moreover, study the kinematics of deformation across the Tibetan Plateau. My results show slip rates ranging from ~2 to ~12 mm/a, highly heterogeneous interseismic fault coupling (fully locked coexist with fully creeping), distinct seismic potential and different earthquake cycles along these faults. In particular, I identify two and one new aseismic creeping segments along the Haiyuan fault system and the Xianshuihe fault respectively. My geodetic observation and modeling results demonstrate the spatio-temporal diversity and complexity of interseismic fault deformation in the Tibetan Plateau, highlight the significance of considering vertical deformation in InSAR, and allow a new and in-depth understanding of earthquake cycles along the above three fault systems.
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yanchuan Li. Geodetic observation and modelling of fault deformation in the Tibetan Plateau. Earth Sciences. Université Côte d'Azur, 2020. English. ⟨NNT : 2020COAZ4002⟩. ⟨tel-03135109⟩

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