Estimating anisotropy parameters and traveltimes in the τ‐p domain

Geophysics ◽  
2002 ◽  
Vol 67 (4) ◽  
pp. 1076-1086 ◽  
Author(s):  
Mirko van der Baan ◽  
J. Michael Kendall
Keyword(s):  
Anisotropic Media ◽  
Seismic Wave Propagation ◽  
Linear Process ◽  
Fast Method ◽  
Forward Modelling ◽  
Interval Estimates ◽  
Taylor Series Expansions ◽  
Local Interval ◽  
Anisotropy Parameters ◽  
And Inversion

The presence of anisotropy influences many aspects of seismic wave propagation and has therefore implications for conventional processing schemes. To estimate the anisotropy, we need both forward modelling and inversion tools. Exact forward modelling in anisotropic media is generally done by raytracing. However, we present a new and fast method, using the τ‐p transform, to calculate exact P and SV reflection moveout curves in stratified, laterally homogeneous, anisotropic media which requires no ray tracing. Results are exact even if the SV‐waves display cusps. In addition, we show how the same method can be used for parameter estimation. Since inversion for anisotropic parameters is very nonunique, we develop expressions requiring only a reduced number of parameters. Nevertheless, predictions using these expressions are more accurate than Taylor series expansions and are also able to handle cusps in the SV traveltime curves. In addition, layer stripping is a linear process. Therefore, both effective (average) and local (interval) estimates can be obtained.

Traveltime and conversion‐point computations and parameter estimation in layered, anisotropic media by τ‐p transform

Geophysics ◽  
2003 ◽  
Vol 68 (1) ◽  
pp. 210-224 ◽  
Author(s):  
Mirko van der Baan ◽  
J.‐Michael Kendall
Keyword(s):  
Ray Tracing ◽  
Transverse Isotropy ◽  
Anisotropic Media ◽  
Forward Modeling ◽  
Seismic Wave Propagation ◽  
Pure Mode ◽  
Fast Method ◽  
Conversion Point ◽  
Arbitrary Strength ◽  
Taylor Series Expansions

Anisotropy influences many aspects of seismic wave propagation and, therefore, has implications for conventional processing schemes. It also holds information about the nature of the medium. To estimate anisotropy, we need both forward modeling and inversion tools. Forward modeling in anisotropic media is generally done by ray tracing. We present a new and fast method using the τ‐p transform to calculate exact reflection‐moveout curves in stratified, laterally homogeneous, anisotropic media for all pure‐mode and converted phases which requires no conventional ray tracing. Moreover, we obtain the common conversion points for both P‐SV and P‐SH converted waves. Results are exact for arbitrary strength of anisotropy in both HTI and VTI media (transverse isotropy with a horizontal or vertical symmetry axis, respectively). Since inversion for anisotropic parameters is a highly nonunique problem, we also develop expressions describing the phase velocities that require only a reduced number of parameters for both types of anisotropy. Nevertheless, resulting predictions for traveltimes and conversion points are generally more accurate than those obtained using the conventional Taylor‐series expansions. In addition, the reduced‐parameter expressions are also able to handle kinks or cusps in the SV traveltime curves for either VTI or HTI symmetry.

Enabling isotropic reflectivity modeling and inversion in anisotropic media

2021 ◽  
Vol 40 (4) ◽  
pp. 267-276
Author(s):  
Peter Mesdag ◽  
Leonardo Quevedo ◽  
Cătălin Tănase
Keyword(s):  
Synthetic Data ◽  
Anisotropic Media ◽  
Forward Modeling ◽  
Seismic Inversion ◽  
Stratified Medium ◽  
Effective Parameters ◽  
Elastic Parameters ◽  
Pp Wave ◽  
Anisotropic Elastic ◽  
And Inversion

Exploration and development of unconventional reservoirs, where fractures and in-situ stresses play a key role, call for improved characterization workflows. Here, we expand on a previously proposed method that makes use of standard isotropic modeling and inversion techniques in anisotropic media. Based on approximations for PP-wave reflection coefficients in orthorhombic media, we build a set of transforms that map the isotropic elastic parameters used in prestack inversion into effective anisotropic elastic parameters. When used in isotropic forward modeling and inversion, these effective parameters accurately mimic the anisotropic reflectivity behavior of the seismic data, thus closing the loop between well-log data and seismic inversion results in the anisotropic case. We show that modeling and inversion of orthorhombic anisotropic media can be achieved by superimposing effective elastic parameters describing the behavior of a horizontally stratified medium and a set of parallel vertical fractures. The process of sequential forward modeling and postinversion analysis is exemplified using synthetic data.

Finite difference forward modelling across the Tyrrhenian basin

2021 ◽  
Author(s):  
Chiara Nardoni ◽  
Luca De Siena ◽  
Fabio Cammarano ◽  
Elisabetta Mattei ◽  
Fabrizio Magrini
Keyword(s):  
Wave Propagation ◽  
Finite Difference ◽  
Wave Attenuation ◽  
Software Tool ◽  
Seismic Wave Propagation ◽  
Tyrrhenian Sea ◽  
Forward Modelling ◽  
Crustal Thinning ◽  
Energy Leakage ◽  
Radiative Transfer Equations

<p>Strong lateral variations in medium properties affect the response of seismic wavefields. The Tyrrhenian Sea is ideally suited to explore these effects in a mixed continental-oceanic crust that comprises magmatic systems. The study aims at investigating the effects of crustal thinning and sedimentary layers on wave propagation, especially the reverberating (e.g., Lg) phases, across the oceanic basin. We model regional seismograms (600-800 km) using the software tool OpenSWPC (Maeda et al., 2017, EPS) based on the finite difference simulation of the wave equation. The code simulates the seismic wave propagation in heterogeneous viscoelastic media including the statistical velocity fluctuations as well as heterogeneous topography, typical of mixed settings. This approach allows to evaluate the role of interfaces and layer thicknesses on phase arrivals and direct and coda attenuation measurements. The results are compared with previous simulations of the radiative-transfer equations. They provide an improved understanding of the complex wave attenuation and energy leakage in the mantle characterizing the southern part of the Tyrrhenian Sea and the Italian peninsula. The forward modelling is to be embedded in future applications of attenuation, absorption and scattering tomography performed with MuRAT (the Multi-Resolution Attenuation Tomography code – De Siena et al. 2014, JVGR) available at https://github.com/LucaDeSiena/MuRAT.</p>

Effects of induced stress on seismic forward modelling and inversion

2018 ◽  
Vol 213 (2) ◽  
pp. 851-867 ◽  
Author(s):  
Jeroen Tromp ◽  
Jeannot Trampert
Keyword(s):  
Forward Modelling ◽  
Induced Stress ◽  
And Inversion

Forward modelling and inversion of self-potential anomalies caused by 2D inclined sheets

2013 ◽  
Vol 44 (3) ◽  
pp. 176-184 ◽  
Author(s):  
Mohamad Sadegh Roudsari ◽  
Ali Beitollahi
Keyword(s):  
Forward Modelling ◽  
And Inversion ◽  
Self Potential

Forward modelling and inversion of multi‐source TEM data

2008 ◽  
Author(s):  
D. W. Oldenburg ◽  
E. Haber ◽  
R. Shekhtman
Keyword(s):  
Forward Modelling ◽  
And Inversion

Wavefront construction modeling and inversion of VSP data for anisotropy parameters

2003 ◽  
Author(s):  
Richard L. Gibson ◽  
Vincent Durussel ◽  
Kyoung‐Jin Lee
Keyword(s):  
Vsp Data ◽  
Anisotropy Parameters ◽  
And Inversion

Mimetic finite-difference coupled-domain solver for anisotropic media

Geophysics ◽  
2021 ◽  
Vol 86 (1) ◽  
pp. T45-T59
Author(s):  
Harpreet Sethi ◽  
Jeffrey Shragge ◽  
Ilya Tsvankin
Keyword(s):  
Finite Difference ◽  
Boundary Conditions ◽  
Model Building ◽  
Fluid Layer ◽  
Anisotropic Media ◽  
Horizontal Displacement ◽  
Solid Boundary ◽  
Ocean Bottom ◽  
Solid Interface ◽  
And Inversion

Accurately modeling full-wavefield solutions at and near the seafloor is challenging for conventional single-domain elastic finite-difference (FD) methods. Because they treat the fluid layer as a solid with zero shear-wave velocity, the energy partitioning for body and surface waves at the seafloor is distorted. This results in incorrect fluid/solid boundary conditions, which has significant implications for imaging and inversion applications that use amplitude information for model building. To address these issues, here we use mimetic FD (MFD) operators to develop and test a numerical approach for accurately implementing the boundary conditions at a fluid/solid interface. Instead of employing a single “global” model domain, we partition the full grid into two subdomains that represent the acoustic and elastic (possibly anisotropic) media. A novel split-node approach based on one-sided MFD operators is introduced to distribute grid points at the fluid/solid interface and satisfy the wave equation and the boundary conditions. Numerical examples demonstrate that such MFD operators achieve stable implementation of the boundary conditions with the same (fourth) order of spatial accuracy as that inside the split-domain interiors. We compare the wavefields produced by the MFD scheme with those from a more computationally expensive spectral-element method to validate our algorithm. The modeling results help analyze the events associated with the fluid/solid (seafloor) interface and provide valuable insights into the horizontal displacement or velocity components (e.g., recorded in ocean-bottom-node data sets). The developed MFD approach can be efficiently used in elastic anisotropic imaging and inversion applications involving ocean-bottom seismic data.

Sign in / Sign up

Export Citation Format

Share Document