Dr. Karl-Josef Sandmeier, Zipser Strasse 1, 76227 Karlsruhe, Germany
Tel. ++49-721-491206, Fax ++49-721-4067994, e-mail: info@sandmeier-geo.de
single shot data
import and geometry setting
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Reflexw modelling
Short overview of the 2D-interpretation tools
©Sandmeier Scientific Software 2012
processing and
interpretation
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Reflexw 2D-dataanalysis
filtering the seismic data
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Reflexw 2D-dataanalysis
picking the first arrivals
create a model of the underground using different methods
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Reflexw 2D-dataanalysis
The 2D seismic shot data are processed within the 2D data-analysis module which includes various possibilities of setting the
geometries
and also all necessary
filter
and
edit
functions. Any kind of line based geoemetry for the shots and the receivers is possible. Some interactive interpretation tools like the
interecepttime method
are included for a very quick interpretation even within the field.
Different kinds of
picking
the first arrivals are included. You have the choice between manual picking, continuous picking and a semi-automatic picking using a phase follower (manual editing is always possible).
1D-interactive modelling
2D-wavefront inversion
refraction tomography
forward
raytracing
forward raytracing
modelling
wavefront-inversion
modelling
perform wavefront inversion
The combined traveltimes are directly inverted into a underground model using the
wavefront inversion method
which allows:
interactive back propagation of the wavefronts using finite differences approximation of the eikonal equation; the backpropagation is exact, even for very complicated overburdens.
inversion of
layer interfaces
and
layer velocities
the
topography
can directly be included in the inversion process
refraction tomography
modelling
The
refraction tomography
allows an automatic inversion of the combined traveltimes. The data coverage must be high enough but no assignment to layers is necessary. The inversion is based on a two-dimensional tomographic approach based on
SIRT
(simultaneous iterative reconstruction technique). The
curved rays
are calculated using a finite difference approximation of the eikonal equation (see forward raytracing). A start model must be defined. The start model may be a simple constant velocity velocity without any pre-informations but may also consists of a complex layered model, e.g. resulting from a previous wavefront inversion. The resulting velocity model is a rasterfile stored in REFLEX-format whereby all possibilities of Reflexw are available for a further interpretation.
The
forward raytracing
method can be used either for a validation of the models derived from the wavefront inversion or from the refraction tomography or it can be used as a trial and error method in order to improve the model or even to construct a model of the underground. The main goal is to calculate the traveltimes of the first arrivals but also reflections from layer boundaries can be built.
The method is based on a
finite difference
approximation of the
eikonal equation
for calculating first arrivals. It takes into the account the existence of different propagation waves like transmitted, diffracted or head waves. Therefore no practical limitation concerning the 2D complexity of the medium is given. The method is very suitable for near surface investigations, because there is no need for approximations concerning the complexity of the models. The wavefronts and therefore the raypaths can be stored and displayed.
The information about the geometry (shot and receiver positions) can automatically be adopted from the shot records or from the traveltime files. Editing, if necessary, is easily possible. The number of shots (e.g. a complete refraction seismic line) is not limited.
combine and assign picked first arrivals
The first part (traveltime processing) contains the possibility to put together the picked traveltimes from several shots and to assign the picks to special layers. There exists nearly no practical limitation for the number of shots and receivers.
