Any P-wave kinematic algorithm for vertical transversely isotropic media can be ADAPTed to moderately anisotropic media of arbitrary symmetry type

Rasolofosaon, Patrick N.J.

doi:10.1016/j.jappgeo.2002.11.003

Cited by 4 publications

(2 citation statements)

References 22 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The combination of such elements of symmetry can result in eight anisotropy systems (e.g., GIBOWICZ and KIJKO, 1994). Transverse Isotropy (TI) is one type of anisotropy that has been extensively studied in soil and rock mechanics (e.g., TSVANKIN, 1996;LIU et al, 2000;RASOLOFOSAON, 2003). The existence of one axis of symmetry in this case, often along the vertical direction (VTI), reduces the number of independent elastic parameters to five.…”

Section: Introductionmentioning

confidence: 99%

Anisotropy Effects on Microseismic Event Location

King

Talebi

2007

Pure appl. geophys.

View full text Add to dashboard Cite

Seismic anisotropy in sedimentary environments is significant-microseismic waveforms often show strong shear-wave splitting, with differences reaching 40% between horizontally and vertically-polarized shear-wave velocities. Failure to account for this anisotropy is shown to result in large microseismic event location errors. A method is presented here for determining the five elastic parameters of a homogeneous, vertical transverse-isotropic (VTI) model from calibration shot data. The method can also use data from mininginduced seismic events, which are then simultaneously located. This simple model provides a good fit to arrival times from coal-environment data, and results in dramatic shifts in interpreted event locations.

show abstract

Section: Introductionmentioning

confidence: 99%

Anisotropy Effects on Microseismic Event Location

King

Talebi

2007

Pure appl. geophys.

View full text Add to dashboard Cite

show abstract

“…This is not prohibitively restrictive because most near‐surface geological media are indeed weakly anisotropic (Thomsen 1986) and can often be presumed horizontally layered (TI). Indeed, using well‐defined transformations, P ‐wave kinematic algorithms for TI media can be transformed to appropriately anisotropic media of arbitrary symmetry type (Rasolofosaon 2003). Mathematical reconstruction of subsurface slowness and the Thomsen parameters (ɛ, δ) aims to minimize the functional characterizing the misfit between observed and predicted overall traveltimes ( t i ), and commonly requires specification of a best‐guess starting model describing the spatial distribution of subsurface slowness.…”

Section: Introductionmentioning

confidence: 99%

Anisotropic seismic inversion using a multigrid Monte Carlo approach

Mewes¹,

Kulessa²,

McKinley

et al. 2010

Geophysical Journal International

View full text Add to dashboard Cite

S U M M A R YWe propose a new approach for the inversion of anisotropic P-wave data based on Monte Carlo methods combined with a multigrid approach. Simulated annealing facilitates objective minimization of the functional characterizing the misfit between observed and predicted traveltimes, as controlled by the Thomsen anisotropy parameters (ε, δ). Cycling between finer and coarser grids enhances the computational efficiency of the inversion process, thus accelerating the convergence of the solution while acting as a regularization technique of the inverse problem. Multigrid perturbation samples the probability density function without the requirements for the user to adjust tuning parameters. This increases the probability that the preferred global, rather than a poor local, minimum is attained. Undertaking multigrid refinement and Monte Carlo search in parallel produces more robust convergence than does the initially more intuitive approach of completing them sequentially. We demonstrate the usefulness of the new multigrid Monte Carlo (MGMC) scheme by applying it to (a) synthetic, noise-contaminated data reflecting an isotropic subsurface of constant slowness, horizontally layered geologic media and discrete subsurface anomalies; and (b) a crosshole seismic data set acquired by previous authors at the Reskajeage test site in Cornwall, UK. Inverted distributions of slowness (s) and the Thomson anisotropy parameters (ε, δ) compare favourably with those obtained previously using a popular matrix-based method. Reconstruction of the Thomsen ε parameter is particularly robust compared to that of slowness and the Thomsen δ parameter, even in the face of complex subsurface anomalies. The Thomsen ε and δ parameters have enhanced sensitivities to bulk-fabric and fracture-based anisotropies in the TI medium at Reskajeage. Because reconstruction of slowness (s) is intimately linked to that ε and δ in the MGMC scheme, inverted images of phase velocity reflect the integrated effects of these two modes of anisotropy. The new MGMC technique thus promises to facilitate rapid inversion of crosshole P-wave data for seismic slownesses and the Thomsen anisotropy parameters, with minimal user input in the inversion process.Subsurface media commonly exhibit seismic anisotropy, caused for example by changes in lithology or stratigraphy, the intensity and pattern of fracturing, preferred mineral alignment or mechanical or fluid processes. It is well known that failure to account for anisotropy can lead to significant errors in tomographic reconstructions of * Formerly at: School of Planning, Architecture, and Civil Engineering, Queen's University Belfast, Belfast BT9 5AG, UK. subsurface slowness using compressional (P-) wave data (Carrion et al. 1992). The Thomsen (1986) parameters (ε, δ), are useful measures of anisotropically propagating P wave fronts in weakly anisotropic media (∼10-20 per cent)

show abstract

Reflection moveout approximations for P-waves in a moderately anisotropic homogeneous tilted transverse isotropy layer

Pšenčı́k

Farra

2017

GEOPHYSICS

View full text Add to dashboard Cite

We have developed approximate nonhyperbolic P-wave moveout formulas applicable to weakly or moderately anisotropic media of arbitrary anisotropy symmetry and orientation. Instead of the commonly used Taylor expansion of the square of the reflection traveltime in terms of the square of the offset, we expand the square of the reflection traveltime in terms of weak-anisotropy (WA) parameters. No acoustic approximation is used. We specify the formulas designed for anisotropy of arbitrary symmetry for the transversely isotropic (TI) media with the axis of symmetry oriented arbitrarily in the 3D space. Resulting formulas depend on three P-wave WA parameters specifying the TI symmetry and two angles specifying the orientation of the axis of symmetry. Tests of the accuracy of the more accurate of the approximate formulas indicate that maximum relative errors do not exceed 0.3% or 2.5% for weak or moderate P-wave anisotropy, respectively.

show abstract

Any P-wave kinematic algorithm for vertical transversely isotropic media can be ADAPTed to moderately anisotropic media of arbitrary symmetry type

Cited by 4 publications

References 22 publications

Anisotropy Effects on Microseismic Event Location

Anisotropy Effects on Microseismic Event Location

Anisotropic seismic inversion using a multigrid Monte Carlo approach

Reflection moveout approximations for P-waves in a moderately anisotropic homogeneous tilted transverse isotropy layer

Contact Info

Product

Resources

About