More details about Rayfract® software
WET Wavepath Eikonal Traveltime tomography models multiple signal propagation paths contributing to
one first break, based on the
Fresnel volume approach.
Conventional ray tracing tomography is limited to the modelling
of just one ray per first break. Also, our
(Lecomte, Gjoystdal et al. Geophysical Prospecting May 2000) used for
traveltime field computation explicitly models diffraction besides refraction
and transmission of acoustic waves. As a consequence the
velocity anomaly imaging capability is enhanced with our WET tomographic
inversion compared to conventional ray tomography.
Our Smooth inversion tomographic method is based on physically
realistic modeling of first break propagation, for P-wave and S-wave surveys. We forward model
refraction, transmission and diffraction (Lecomte, 2000) and
back-project traveltime residuals along wave paths, also known as
Fresnel volumes (Watanabe, 1999) instead of conventional rays. This
increases the numerical robustness of the inversion. A smooth minimum-structure and artefact-free 1D starting model is
determined automatically directly from the seismic traveltime data, by
horizontally averaging DeltatV (Wiechert-Herglotz) method
1D velocity-depth profiles along the seismic line. The starting model is then refined with 2D
WET Wavepath Eikonal Traveltime inversion (Schuster, 1993). We use an adapted
for velocity update of grid cells, when back-projecting traveltime residuals along wavepaths
(Schuster, 1993) and
Rayfract® supports any surface based 2D recording geometry,
including roll-along seismic reflection lines. Up to 500 shots may be imported
into the same 2D profile database. These shots may be recorded with just one
or with multiple
overlapping receiver spreads.
10 or more shots per receiver spread are recommended. The spacing of adjacent
receivers may vary along the same user-defined
receiver spread type. We support
from 12 up to 360 channels per receiver spread. 24 or more channels are recommended. Supports many
input data formats.
Import shots interactively, our with our
.HDR batch import.
Review our SAGEEP 2010 manual
function key help). Allows
bidirectional frequency filtering of traces,
with single-pole or Chebyshev-Butterworth filter. Pick first breaks interactively for each trace,
or use our polyline picker, combined with automatic picking.
Pick shear wave first breaks in Trace|Shot point gather, for shot pairs with same
shot position but reversed trace polarity.
Check your picks for reciprocal traveltime errors
in Trace|Offset gather display. Shift picks for all traces of same shot with trigger delay correction.
We support the conventional, layer-based refraction seismic
Plus-Minus method (J.G. Hagedoorn 1959) and the
(E. Brueckl 1987 and
Glyn M. Jones and D.B. Jovanovich 1985). Our Wavefront method uses a laterally varying XY
receiver separation, and is an optimized version of the
GRM Generalized Reciprocal Method
(Palmer 1980 and 1981).
Map traveltimes to refractors interactively or semi-automatically.
WET inversion does not require mapping traveltimes to refractors.
plotting of 1.5D refractors obtained with layer-based methods on 2D WET tomograms.
Supports Smooth inversion of borehole surveys with constant-velocity starting model, for
reverse VSP and
uphole refraction surveys.
Uses multiple CPU cores, for fast parallel forward modeling
of traveltimes and back-projection of residuals along wave paths (Fresnel volumes), with SIRT algorithm.
Shots positioned at the bottom of deep holes located on the 2D
seismic profile, i.e., "uphole" shots, may be recorded with the same receiver
spread layouts as surface-based shots. First breaks picked for these uphole
shots are used to constrain the WET tomography.
Convert walkaway VSP surveys
into uphole refraction surveys with our software and then use the resulting
GeoTomCG .3DD with simulated uphole shots to
WET tomography. Or process uphole shots from two or more boreholes into one
common, surface-based receiver/hydrophone spread as a
reverse VSP survey and
horizontal borehole survey,
without surface-based refraction shots.
The software handles extreme topography and allows computation
of velocity vs. two-way time for reflection processing, i.e., for static
corrections. Golden Software Surfer is required for
automatic imaging and plotting of XTV and WET tomography output.
You may download a free demo from
http://www.goldensoftware.com. This is
print-disabled, and edited tomogram plots can't be saved. But otherwise this works
fine, for on-the-fly automatic creation of tomogram plots with our software, from
computed Surfer .GRD velocity grid files.
pseudo-3D fence diagrams
with Golden Software Voxler. You can import Surfer .GRD grids VELOITXY.GRD
generated with our software, into Voxler.
For further details, please check our
.pdf reference chapters
"System limitations", "Seismic and header data import" etc. You are welcome to
send us a test profile for free interpretation.
Copyright © 1996-2018
Intelligent Resources Inc. All rights reserved. RAYFRACT® is a registered trademark
of Intelligent Resources Inc. in Canada and Switzerland.