Seismic anisotropy is the variation of seismic wavespeed with direction. Seismic anisotropy is an indicator of long range order in a material, where features smaller than the seismic wavelength (e.g., crystals, cracks, pores, layers or inclusions) have a dominant alignment. This alignment leads to a directional variation of elasticity wavespeed.
Isotropic refers to the properties of a material which is independent of the direction whereas anisotropic is direction-dependent. These two terms are used to explain the properties of the material in basic crystallography. The mechanical and physical properties can be easily affected based on the atom orientation in crystals.
For a crystal of a mineral, variation in physical properties observed in different directions is anisotropy. In rocks, variation in seismic velocity measured parallel or perpendicular to bedding surfaces is a form of anisotropy. Often found where platy minerals such as micas and clays align parallel to depositional bedding as sediments are compacted, anisotropy is common in shales. Synonyms.Anisotropy is most easily observed in single crystals of solid elements or compounds, in which atoms, ions, or molecules are arranged in regular lattices. In contrast, the random distribution of particles in liquids, and especially in gases, causes them rarely, if ever, to be anisotropic. Read More on This Topic mechanics of solids: Anisotropy.Anisotropy is also used to describe situations where properties vary systematically, dependent on direction. Isotropic radiation has the same intensity regardless of the direction of measurement, and an isotropic field exerts the same action regardless of how the test particle is oriented.
The most common type of anisotropy that one deals with in seismic data is polar anisotropy (transverse isotropy). Media with vertical (VTI), tilted (TTI), and horizontal (HTI) axes have been shown to exist as a result of sedimentary deposition or fracturing.Read More
Anisotropy and Isotropy. Amorphous solids are said to be isotropic, and crystalline solids are anisotropic for their physical property measurements. Isotropy comes from the Greek word; iso means same and tropos means direction. The name rightly indicates that for the amorphous solids; the physical property measurements are same in all the directions. The same correlation applies for anisotropy.Read More
Really the anisotropy will require almost 21 material constants for the material definition in an FE software. Then orthotropic materials will need 9 constants in 3 planes of symmetry. A simplified.Read More
Assumptions about isotropy began to crack as early as the 1930s, when measure-ments made with electrodes laid in different directions on the earth’s surface were seen to give different results when strata were dip-ping than when strata were flat.2 In geo-physics, the introduction of shear wave sources in mid-1970s showed that shear wave anisotropy was often significant and could be analyzed.Read More
Contemporary depth imaging projects often require the final preSDM image to be converted to time for comparison to vintage preSTM products. In this tutorial, I consider the situation where we have performed an anisotropic TTI preSDM and want to compare it to say an anisotropic preSTM. Such a comparison is inherently invalid, as time-migration will explicitly treat any anisotropy as if it were.Read More
Shales are notorious for their strong elastic anisotropy, so-called, vertical transverse isotropy or VTI. This VTI anisotropy is of practical importance as it is required for correct surface seismic data interpretation, seismic to well tie and azimuth versus offset analysis. A number of competing factors are responsible for VTI anisotropy in shales, namely, (1) micro-scale elastic anisotropy.Read More
Anisotropy is the property of being directionally dependent, as opposed to isotropy, which means homogeneity in all directions.It can be defined as a difference in one soil physical property along different directions. Anisotropic soil does not have the same physical properties when the direction of measurement is changed. Commonly it is used in reference to soil structure, soil strength, and.Read More
A common requirement for spatial modeling is the development of an appropriate correlation structure. Although the assumption of isotropy is often made for this structure, it is not always appropriate. A conventional practice when checking for isotropy is to informally assess plots of direction-specific sample (semi)variograms. Although a.Read More