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Fracture estimation in anisotropic media
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|Title:||Fracture estimation in anisotropic media|
|Authors:||Hood, Julie A.|
|Keywords:||Geology, Structural -- Mathematical models|
Submarine geology -- Mathematical models
|Abstract:||A heterogeneous mixture of isotropic elements may appear homogeneous and anisotropic when the scale of its fabric is smaller than the seismic wavelengths that measure it. This fabric can result from thin layering, aligned crystals, anisotropic background stress, aligned fractures, and/or oriented microcracks. Horizontal layering in sedimentary basins and the oceanic crust generates transverse isotropy, a hexagonal symmetry with a vertical symmetry axis, an extremely common form of anisotropy. The elastic properties of transversely isotropic media do not vary with azimuth. With the advent of multi-component seismometers and walk-around experiments, however, azimuthal variation is now frequently observed as well. This azimuthal anisotropy usually results from steeply dipping aligned fractures or microcracks. Realistic earth models must include all the significant constituent anisotropies of fracture systems and the backgrounds in which these fracture systems are embedded. The anisotropy increases in complexity as the number of different systems incorporated into the medium increases. Considering all possible combinations of constituents, a variety of anisotropies can result. For example, embedding a fracture system into an isotropic background can produce anisotropy with a symmetry as simple as hexagonal or as complex as triclinic. Analysis of either fractures or the background requires separating the two anisotropic effects otherwise they interfere. As long as there is at least one symmetry plane in fractured anisotropic media, the contribution of the fractures to the elastic modulus matrix of the background can be removed. The fracture properties can be evaluated by imposing the background symmetry constraints. Once the fracture compliances are obtained, the elastic properties of the unfractured background and the complexity of its symmetry can be determined.|
Thesis (Ph. D.)--University of Hawaii at Manoa, 1990.
Includes bibliographical references (leaves 44-45)
vii, 45 leaves, bound ill. 29 cm
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|Appears in Collections:||
Ph.D. - Geology and Geophysics|
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