Polar anisotropy from walkway VSPs

2008 ◽  
Vol 27 (10) ◽  
pp. 1242-1250 ◽  
Author(s):  
W. Scott Leaney
Keyword(s):  
Polar Anisotropy

scholarly journals Some Considerations of the Polar-Anisotropy and its Application to the Winding Package

1960 ◽  
Vol 26 (164) ◽  
pp. 558-566 ◽  
Author(s):  
Toshio NISHIHARA ◽  
Kiyohisa FUJINO ◽  
Tsuneo HIRAI ◽  
Shin TSUKUMA
Keyword(s):  
Polar Anisotropy

Effect of Polar Anisotropy of Wood Loaded Perpendicular to Grain

2001 ◽  
Vol 13 (1) ◽  
pp. 2-9 ◽  
Author(s):  
Simon Aicher ◽  
Gerhard Dill-Langer ◽  
Lilian Höfflin
Keyword(s):  
Polar Anisotropy

Diffraction traveltime approximation for general anisotropic media

Geophysics ◽  
2013 ◽  
Vol 78 (5) ◽  
pp. WC15-WC23 ◽  
Author(s):  
Sergius Dell ◽  
Anna Pronevich ◽  
Boris Kashtan ◽  
Dirk Gajewski
Keyword(s):  
Anisotropic Medium ◽  
Seismic Anisotropy ◽  
Polar Anisotropy ◽  
Isotropic Media ◽  
Diffraction Imaging ◽  
Resolution Imaging ◽  
Anisotropy Parameters ◽  
Homogeneous Media ◽  
Derivatives Of ◽  
Independent Parameters

Diffractions play an important role in seismic processing because they can be used for high-resolution imaging and the analysis of subsurface properties like the velocity distribution. Until now, however, only isotropic media have been considered in diffraction imaging. We have developed a method wherein we derive an approximation for the diffraction response for a general 2D anisotropic medium. Our traveltime expression is formulated as a double-square-root equation that allows us to accurately and reliably describe diffraction traveltimes. The diffraction response depends on the ray velocity, which varies with angle and thus offset. To eliminate the angle dependency, we expand the ray velocity in a Taylor series around a reference ray. We choose the fastest ray of the diffraction response, i.e., the ray corresponding to the diffraction apex as the reference ray. Moreover, in an anisotropic medium, the location of the diffraction apex may be shifted with respect to the surface projection of the diffractor location. To properly approximate the diffraction response, we consider this shift. The proposed approximation depends on four independent parameters: the emergence angle of the fastest ray, the ray velocity along this ray, and the first- and second-order derivatives of the ray velocity with respect to the ray angle. These attributes can be determined from the data by a coherence analysis. For the special case of homogeneous media with polar anisotropy, we establish relations between anisotropy parameters and the parameters of the diffraction operator. Therefore, the stacking attributes of the new diffraction operator are suitable to determine anisotropy parameters from the data. Moreover, because diffractions provide a better illumination than reflections, they are particularly suited to analyze seismic anisotropy at the near offsets.

P-SV reflection moveouts for transversely isotropic media with a vertical symmetry axis

Geophysics ◽  
1991 ◽  
Vol 56 (8) ◽  
pp. 1271-1274 ◽  
Author(s):  
A. J. Seriff ◽  
K. P. Sriram
Keyword(s):  
Symmetry Axis ◽  
Short Note ◽  
Transversely Isotropic ◽  
Isotropic Layer ◽  
Numerical Examples ◽  
The Real ◽  
Polar Anisotropy ◽  
Transversely Isotropic Media ◽  
Isotropic Media ◽  
Transversely Isotropic Layer

In a recently published short note, F. K. Levin (1989) discusses the relation between the “moveout velocities” of P-P, P-SV, and SV-SV reflections from the bottom of a transversely isotropic layer with a vertical symmetry axis. We refer to such a medium as one exhibiting “polar anisotropy.” Levin’s note was prompted by a paper of Tessmer and Behle (1988), and it is relevant to a paper by Iverson and others (1989), both of which discuss the computation of shear velocities from moveout velocities obtained with P-P and P-S reflections. Levin’s note addresses the practically important question of the use of this method in the presence of polar anisotropy, a phenomenon which we believe occurs almost universally in the sedimentary layers of the real earth. Levin suggests that polar anisotropy of “typical” magnitude must be considered in this problem. He uses as an estimate of typical magnitudes data given by Thomsen (1986) and concludes from numerical examples that the method of estimating shear velocities proposed by Tessmer and Behle and by Iverson may be subject to unacceptably large errors in many real cases. Moreover, Levin suggests that the source of these errors is mysterious.

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