Earthquakes, groundwater and surface deformation : exploring the poroelastic response to megathrust earthquakes




McCormack, Kimberly Alison

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This thesis explores the poroelastic effects of large subduction zone earthquakes using numerical models and a variety of datasets with the overarching goal of beginning to deconvolve post-seismic geodetic deformation signals -- while exploring other interesting phenomena involving the poroelastic response to earthquakes along the way. Chapter 1 sets up an elastic inverse problem used to derive the initial slip condition. We formulate an adjoint-based inversion methodology to solve for the initial condition of the coupled poroelastic forward model within a consistent, finite element framework. Chapter 2 discusses the broad hydrological effects of large subduction zone earthquakes both in general and the predicted hydrological effects of the 2012 7.6 M [sunscript w] Nicoya Peninsula earthquake. It explores how different hydro-mechanical parameters affect both the instantaneous and time-dependent response and touches on some of the limitations of the models. Chapter 3 focuses on the potential effect of poroelastic deformation on post-seismic geodetic signals. Here we look at the relationships between the co-seismic pore pressure changes and different components of poroelastic deformation. It then compares the modeled surface deformation timeseries to the measured deformation at a number of GPS stations. The last chapter walks through the suite of models and data interpolation functions included in the open source toolbox built during this project.


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