Most bulk elastic media are weakly anisotropic. The equations governing weak anisotropy much simpler than those strong anisotropy, and they easier to grasp intuitively. These indicate that a certain anisotropic parameter (denoted δ) controls most phenomena of importance in exploration geophysics, some which nonnegligible even when the is weak. critical δ an awkward combination parameters, totally independent horizontal velocity may be either positive or negative natural contexts.

The standard hyperbolic approximation for reflection moveouts in layered media is accurate only relatively short spreads, even if the layers are isotropic. Velocity anisotropy may significantly enhance deviations from moveout. Nonhyperbolic analysis anisotropic also important because conventional moveout processing on spreads insufficient to recover true vertical velocity (hence depth). We present analytic and numerical of combined influence transverse isotropy layering long‐spread moveouts....

Abstract All theoretical expressions which relate the characteristics of saturated aligned cracks to associated elastic anisotropy are restricted in some important way, for example case stiff pore fluids, or absence equant porosity, a moderately high frequency band. Because these restrictions, previous theory is not suitable application upper crust, where fluid brine (K f ≅ K 8 20) , porosity often substantial (φ p > 0.1), and band sonic seismic. This work removes particular recognizing...

Recent surveys have shown that azimuthal anisotropy (due most plausibly to aligned fractures) has an important effect on seismic shear waves. Previous work had discussed these effects VSP data; the same are seen in surface recording of reflections at small moderate angles incidence. The anisotropic different polarization components vertically traveling waves permit recognition and estimation very degrees (of order ⩾1 percent), as interferometer. Anisotropic traveltime yield estimates which...

Converted‐wave processing is more critically dependent on physical assumptions concerning rock velocities than pure‐mode processing, because not only moveout but also the offset of imaged point itself depend upon parameters medium. Hence, unrealistic homogeneity and isotropy are critical for propagation, where image‐point determined geometrically rather physically. In layered anisotropic media, an effective velocity ratio [Formula: see text] (where average vertical γ 2 corresponding...

Recent advances in parameter estimation and seismic processing have allowed incorporation of anisotropic models into a wide range methods. In particular, vertical tilted transverse isotropy are currently treated as an integral part velocity fields employed prestack depth migration algorithms, especially those based on the wave equation. We briefly review state art modeling, processing, inversion data for media. Topics include optimal parameterization, body-wave modeling methods, P-wave...

The semiphenomenological Biot‐Gassmann (B-G) formulation of the low‐frequency elastic moduli porous rocks does contain two well‐known predictions: (1) shear modulus an unsaturated rock (which is permeated by a compressible fluid, e.g., gas) identical to that same saturated with liquid, and (2) bulk differs from defined amount. These predictions are tested ultrasonic data on large number sedimentary approximately verified, despite evident frequency discrepancy. B-G theory makes only minimal...

Consistency of high temperature equation state solids, considering Gruneisen parameter and lattice dynamics

The gradients of density and temperature within the upper mantle are considered from a thermodynamic point view, Limits for these corresponding to range material properties found in oxides given which indicate: (1) shear velocity minimum does not necessarily imply minimum; (2) gradient is considerably smaller than that indicated by classical Bullen A model; (3) existing estimates thermal profile may be need slight upward adjustment.

This paper presents new theoretical expressions for the elastic velocities (of a cubic or isotropic homogeneous solid) as functions of density and temperature (equations 7 8). These equations have been derived within fourth-order anharmonic theory, i.e., extension theory lattice dynamics into regime finite strain, they include implicitly effects noncentral forces, distant-neighbor interaction, thermal vibration. Application to garnet, spinel, olivine (considered Voigt-Reuss-Hill bodies)...

In anisotropic media, the short‐spread stacking velocity is generally different from root‐mean‐square vertical velocity. The influence of anisotropy makes it impossible to recover (or reflector depth) using hyperbolic moveout analysis on short‐spread, common‐midpoint (CMP) gathers, even if both P‐ and S‐waves are recorded. Hence, we examine feasibility inverting long‐spread (nonhyperbolic) reflection moveouts for parameters transversely isotropic media with a symmetry axis. One possible...

The presence of vertically oriented fractures and/or unequal horizontal stresses has created an azimuthally anisotropic earth, in which shear‐wave (SH) data collected along the principal axes anisotropy display time and reflection amplitude anomalies. Amoco shot two crossing lines that were approximately parallel to orthogonal azimuthal anisotropy. At tie point, these SH a time‐variant mis‐tie. point also displays reflection‐coefficient anomalies, attributable dependent velocities. Field...

ABSTRACT P‐wave seismic reflection data, with variable offset and azimuth, acquired over a fractured reservoir can theoretically be inverted for the effective compliance of fractures. The total rock, which is described using second‐ fourth‐rank fracture tensors, represented as background plus additional due to Assuming monoclinic or orthotropic symmetry (which take into account layering multiple sets), components tensors used attributes related characteristics medium. Synthetic tests...

Abstract Complex shear wave splitting (SWS) patterns in subduction zones are often interpreted geodynamically as resulting from complex mantle flow; however, this may not always be necessary. We analyzed 7,093 high‐quality SWS measurements teleseismic S waves recorded by Hi‐net stations across the Ryukyu arc Japan. Our findings show a systematic rotation of fast polarization trench‐parallel to trench‐perpendicular depending on earthquake backazimuth. For same earthquake, measured also vary...

The classic paper by Brown and Korringa, giving the dependence of elastic properties a porous rock on compressibility pore fluid, has been understood for almost 50 years to be generalization (to non-homogeneous solid) earlier work similar topic Gassmann. However, this understanding is based single passage their paper, which contains logical error, so not valid. primary result an additional parameter (compared Gassmann), correct as written in 1975 all isotropic rocks (with one or many...

Variations of reflection amplitude with offset and azimuth are sensitive to the presence natural induced fractures. We tested inversion for fracture compliance matrix components from wide noisy synthetic PP-reflection data. The model was a fractured reservoir monoclinic symmetry, formed by two sets vertical asymmetric fractures embedded in VTI background. (joints) were assumed be vertical, noncircular shape and/or shear compliance. Results showed that an incorrect assumption about symmetry...