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SPIN ESR 3.2: Numerical models across the scales


Name: Zihua Niu drawing

Institution: Ludwig-Maximilian-University Munich, Germany (LMU)

Email: zniu@geophysik.uni-muenchen.de


Introduction

I come from China with a Bachelor in Geotechnical engineering. There I gained my special interests in different fields of continuum mechanics, e.g. elasticity, plasticity, viscosity, fluid mechanics, soil mechanics, thermo-poro-elasticity, fracture mechanics etc..

Afterwards, I went to ETH Zurich for a MSc in Geophysics. I took the time in Zurich for different numerical methods for solving different types of Partial Differential Equations (PDE), e.g. FDM, FEM, FVM, LBM. I also got the chance to work in the lab to understand better how the models may be constrained in practice. The specific techniques employed were Acoustic Emission (for seismic source inversion) and Fiber Opitics (for distributed strain measurement).

I joined LMU Munich in 2021 as a PhD student in Computational Seismology under the supervision of Prof. Heiner Igel and Prof. Alice-Agnes Gabriel. My current research concerns the propagation of seismic waves in nonlinear materials (a type of nonlinear hyperbolic PDEs). The principal method that I may use is the Discontinuous Galerkin Method. The major goal of my research is to develop a parallelized code for large scale wave propagation in nonlinear rheology. May you get to know more about my research here.


Publication

Niu, Z., Li, Q., Moradian, O. (2023), Moment Tensor and Stress Inversion Solutions of Acoustic Emissions during Compression and Tensile Fracturing in Crystalline Rocks. Journal of Rock Mechanics and Geotechnical Engineering (Accepted).

Niu, Z., Gabriel, A. A., May, D., Sens-Schönfelder, C., & Igel, H. (2022). A Discontinuous-Galerkin approach to model non-classical nonlinearity observed from lab to global scales (No. EGU22-10523). Copernicus Meetings.

Niu, Z. (2021). Experimental study on the seismic and aseismic deformation during the failure of granitic rock (Master’s thesis).

Niu, Z., Shen, J., Wang, L., & Yang, R. (2019). Thermo-poroelastic modelling of cement sheath: pore pressure response, thermal effect and thermo-osmotic effect. European Journal of Environmental and Civil Engineering, 26(2), 657-682.


Research progress

Implementation and verification of nonlinear models for solid wave propagation with the discontinuous Galerkin method.

Amplitude- and frequency-dependent damage from the current model and from measurements by Manogharan et al. (2021).

Comparing modelling results of two nonlinear models with the lab data.

Inversion of model parameters with the Markov chain Monte Carlo method.