Processing of seismic data in the presence of elliptical anisotropy [microform]
- Bib ID:
- 3283203
- Format:
- Book and Microform
- Author:
- Uren, Norman Frederick
- Description:
- 198 p.
- Summary:
-
Most of the rocks of the earth are anisotropic to some extent. That is, their physical properties, including the velocity of sound in them, vary with direction. Elliptical anisotropy is the term used when the seismic wavefront spreading from a point source of acoustic energy is elliptical in shape. Basic wavefront shape is shown to influence significantly the performance of a wave for the purpose of seismic imaging. The consequences of elliptical and non-elliptical anisotropy on normal moveout (NMO), dip moveout (DMO) and migration are investigated in this thesis by numerical and physical modeling. An anisotropic migrator's equation is developed, suitable for both elliptical and non-elliptical waves, and the performance of this new method is demonstrated. The bulk of the situations encountered in exploration seismology involve transverse isotropy. When a medium is transversely isotropic, SH waves exhibit elliptical anisotropy, while P waves usually are non-elliptical.
The case of transverse isotropy is used in this thesis for the practical comparison of elliptically and non-elliptically anisotropic waveforms. It is shown that elliptical waves have a constant normal moveout velocity in a common mid-point gather. In contrast to common belief, NMO velocity is not in general the horizontal component of the anisotropic velocity function. Non-elliptically anisotropic P waves are shown to have NMO velocities which vary with offset, and common reflection points only occur in common mid-point gathers under special cases of symmetry. Velocity-independent dip moveout correction is shown to work only for elliptical anisotropy. Thus conventional processing such as common mid-point stacking and dip moveout correction are not valid for the commonly used non-elliptical P waves of seismic exploration when anisotropy is present. The zero offset anisotropic migrator's equation developed in this thesis is implemented with a modified Stolt F-K migration approach.
Travel time methods and Fermat's principle are applied to compute numerical reflection time data. Physical model data are also collected for both P and SH waves in a transversely isotropic medium. These data are then migrated with an anisotropic zero offset migration computer program to demonstrate the recovery of the original structure with this new procedure.
- Notes:
-
- (UnM)AAI9101924
- Source: Dissertation Abstracts International, Volume: 51-08, Section: B, page: 3748.
- Chairman: John A. McDonald.
- Thesis (Ph.D.)--University of Houston, 1989.
- Reproduction:
- Microfiche. Ann Arbor, Mich.: University Microfilms International.
- Subject:
- Geophysics
- Other authors/contributors:
- University of Houston
- Copyright:
-
In Copyright
Contact us for information about copying.
Copyright status was determined using the following information:
- Material type:
- Literary Dramatic Musical
- Published status:
- Unpublished
- Creation date:
- 1989
Copyright status may not be correct if data in the record is incomplete or inaccurate. Other access conditions may also apply. For more information please see: Copyright in library collections.
Request this item
Request this item to view in the Library’s reading room.