Hao XieFollow

Date of Completion

5-9-2014

Embargo Period

5-9-2014

Keywords

Anisotropy, surface wave, dispersion, multi-mode, simulated annealing

Major Advisor

Lanbo Liu

Associate Advisor

Benjamin E. Barrowes

Associate Advisor

John W. Lane

Associate Advisor

Amvrossios C. Bagtzoglou

Associate Advisor

Vernon F. Cormier

Field of Study

Civil Engineering

Degree

Doctor of Philosophy

Open Access

Open Access

Abstract

In a wide range of geophysical problems, the mismatch between theoretical prediction and observation may be caused by lacking the consideration of medium anisotropy. Ever increasing accuracy and scale of geophysical field observations require inclusion of anisotropy now. This PhD dissertation focuses on extracting anisotropic earth structure using simulated annealing (SA) inversion of seismic waves.

In the first part of this dissertation, the nature of seismic anisotropy, the dispersion properties of surface waves with the consideration of material anisotropy, and the stochastic inversion using SA are reviewed with certain algorithm development. In Chapter 2 the generalized Hooke’s law is presented with all information of anisotropy contained in independent elastic components of the stiffness matrix. The stiffness matrix in the medium with different symmetric systems is discussed, especially in the vertical transverse isotropy (VTI) medium. In Chapter 3 the dispersion equations of Rayleigh wave and Love wave are derived for the VTI medium. A graphic-based method is proposed to extract dispersion curves. The impact of anisotropy on dispersion curves is discussed, showing that inclusion of multiple modes is critical to the inversion of anisotropy. Chapter 4 studies the stochastic inversion using SA. Considering the initial-model independence and different parameter sensitivities, the very fast simulated annealing (VFSA) is chosen to invert the velocity structure and the anisotropy structure simultaneously. The synthetic example shows the feasibility and effectiveness of this approach.

Four geophysical applications using VFSA inversion compose the second part of this dissertation. As the application to petroleum exploration, Chapter 5 describes the material anisotropy estimation at well location using joint-tomography inversion and VFSA inversion. As the application to the near-surface structure characterization, Chapter 6 studies the velocity and anisotropy structure at the site of Rentschler field, CT with VFSA inversion of multi-mode Love wave extracted from the active source. Chapter 7 studies the near-surface structure at Haddam Meadows, CT with VFSA inversion of multi-mode Rayleigh wave extracted from ambient noise. As the last application, Chapter 8 discusses the mechanical properties of polar firn in Greenland ice sheet from a seismic refraction survey and the inversion of Rayleigh wave dispersions.

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