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COSEISMIC AND POSTSEISMIC DEFORMATION OF 2011 MW 9 TOHOKU EARTHQUAKE - A NONLINEAR INVERSION OF GPS DATA
AdvisorKreemer, Corné W.
Geological Sciences and Engineering
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On March 11, 2011, a magnitude Mw = 9.0 megathrust occurred off the Tohoku coast near the Japan trench. This thesis studies the coseismic and postseismic deformation of the earthquake based on the Global Positioning System (GPS) observations. GPS position time series are modeled to extract coseismic and postseismic displacements. Coseismic displacements are used to invert for coseismic slip. A nonlinear algorithm called Occam's algorithm is employed to invert for the rake of the fault slip (83 ◦ ). For postseismic deformation, the coupled effect of afterslip and viscoelastic are considered. Nonlinear parameters such as the viscosity of the lower crust and the uppermost mantle (10E18.9 ≈ 7.9×10 18 Pa·s), the elastic thickness (51 km), and the rake of fault slip (83 ◦ ) are found with the same nonlinear inversion algorithm. Different components of deformation caused by different mechanisms of deformation are computed, and the results show that afterslip dominates in the first 100 days after the mainshock and the viscoelastic relaxation dominates in the later days of the postseismic deformation.