Zheng, Yingcai2020-01-06May 20192019-05May 2019https://hdl.handle.net/10657/5791Fractures impact reservoir management, drilling, and well completion. Therefore, we characterize fractures systems to understand subsurface stress and flow fields. I studied four topics on fracture characterization for both applied and earthquake seismology: (1) the effect of fractured reservoir layer thickness on reflected P wave amplitudes; (2) the effect of fractured reservoir layer thickness on shear-wave splitting; (3) the effect of normal and tangential fracture compliances on anisotropy and shear wave splitting; and (4) the effect of incidence angle and subducting slab dipping angle on the transmitted seismic wavefield. I considered a 3-layer model in which the middle layer is anisotropic. I applied full-wave modeling based on plane wave expansion in anisotropic media. The modeling includes all reflections and mode conversions. In topic 1, I studied how layer thickness affects the reflected P wave amplitude variation versus azimuth caused by an incident P plane wave in an HTI fractured layer. I found that to accurately extract fracture orientation and density using azimuthal P-wave traveltime as a function of azimuth, the thickness of the fractured reservoir layer cannot be less than the P wavelength. In topic 2, I found that the splitting time for reflected shear waves is related to the thickness of the fractured layer. To observe splitting from seismic data, the layer thickness needs to be ~5 times the S wavelength. In topic 3, I used linear-slip boundary conditions to represent fractures. I found that shear wave splitting is only affected by the tangential compliance, Z_T, because the Thomsen’s parameter, γ, only relates to tangential compliance, Z_T, and not the normal compliance, Z_N. From my modeling, I find it difficult to observe shear wave splitting from synthetic seismic data if the Z_N/Z_T is low (<0.4) even if the fracture thickness is thick enough. In topic 4, I extracted polarization, ϕ, of the fast S wave and the time delay, dt, between the fast and slow S waves measured from seismic records to characterize the possible anisotropy in subducted slabs. I found that ϕ and dt are related to the anisotropic property, the slab dipping and incidence angles.application/pdfengThe author of this work is the copyright owner. UH Libraries and the Texas Digital Library have their permission to store and provide access to this work. Further transmission, reproduction, or presentation of this work is prohibited except with permission of the author(s).Fracture behaviorForward modelingAnisotropyShear-wave splittingSubducting slab2020-01-06Thesisborn digital