Seismic reflection moveout for azimuthally anisotropic media

Anisotropy can exist in the subsurface as an intrinsic property, or as an induced property, or as a combination of both. Induced anisotropy can result due to preferred orientation of grains, thin layering, and/or the presence of fractures. In this thesis, we study the reflection moveout for Compressional and Shear waves in horizontally stratified azimuthally anisotropic media. Reflection moveout in common-midpoint (CMP) gathers is generally treated by an azimuthally-isotropic hyperbolic equation. Recently, special treatment for the reflection moveout in azimuthally anisotropic media has been introduced due to the fact that the moveout in such cases is azimuthally dependent. Here, the normal moveout (NMO) equation parameterized by the exact normal-moveout (NMO) velocity is studied. We verify numerically (through synthetic data) the accuracy of the exact (i.e., analytic) azimuthal description of the NMO velocity. We show that the azimuthal variation of the NMO velocity has, in general, a relatively simple elliptical form. We also show that the NMO equation is sufficiently accurate for P- and Shear-wave propagation on conventional spreadlengths (e.g., lenghts close to the reflector depth). The influence of anisotropy causes the deviation of the moveout curve from a hyperbola, even in a homogeneous anisotropic layer with a horizontal interface. Hence, reflection moveout in azimuthally anisotropic media is not only azimuthally dependent but it is also nonhyperbolic.

Department dc:contributor.department

Massachusetts Institute of Technology. Dept. of Earth, Atmospheric, and Planetary Sciences.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2002

Author dc:creator

• Al-Dajani, AbdulFattah A

Advisor dc:contributor.advisor

• M. Nafi Toksöz.

• Earth, Atmospheric, and Planetary Sciences.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/8057

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/8057