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Constraining the Mantle's Rheology Using Methods in Uncertainty Quantification


Ratnaswamy, Vishagan (2019) Constraining the Mantle's Rheology Using Methods in Uncertainty Quantification. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/F6FW-T648.


An accurate estimation of the large-scale forces in the mantle has been difficult to obtain as numerical models either do not use an accurate rheology nor reproduce surface observations. While much work has been done in developing high-fidelity forward models that capture the salient physics of shear-thinning and dynamic weakening, they fail to reproduce observations such as plate motions and topography. In this thesis, we develop an optimization methodology that minimizes the misfit in surface observations such as plate motions and average effective viscosity for certain regions of the mantle. We utilize adjoints to calculate the gradient, while using second-order adjoints to construct the Hessian so as to infer the rheological parameters of the mantle's rheology. Furthermore, we build on this optimization scheme by constructing the Gaussian approximation of the posterior distribution for the inferred rheological parameters using the Hessian and establish the trade-offs between each parameter through their conditional distributions. We further extend this Gaussian approximation to infer extrinsic quantities such as the stresses in the fault zones and the average effective viscosity in the hinge zones to not only quantify the uncertainty, but also to see partitioning of the coupling of each subduction zone.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:Uncertainty Quantification, Optimization, Computational Geodynamics, Non-Newtonian Fluid Mechanics, Statistical Learning, Subduction Zones, Great Earthquakes
Degree Grantor:California Institute of Technology
Division:Engineering and Applied Science
Major Option:Aeronautics
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Gurnis, Michael C.
Thesis Committee:
  • Meiron, Daniel I. (chair)
  • Ravichandran, Guruswami
  • Simons, Mark
  • Gurnis, Michael C.
Defense Date:23 October 2018
Record Number:CaltechTHESIS:05132019-143045769
Persistent URL:
Ratnaswamy, Vishagan0000-0002-2371-807X
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:11514
Deposited By: Vishagan Ratnaswamy
Deposited On:29 May 2019 20:20
Last Modified:16 Jan 2021 00:51

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