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The Simple Modelling module computes kinematic (travel-time) synthetic data for a user-defined layer model. Given an input layer vector that describes the geometry and velocity of a set of reflectors, the module calculates hyperbolic reflection travel-time curves for a 2D acquisition geometry defined by the grid and source-receiver parameters. The output is a velocity gather and a travel-time vector that can be used for geometry QC, initial velocity model validation, and first-break picking comparison.
Unlike full waveform modelling approaches, this module only computes arrival times (kinematic modelling) — it does not generate seismic amplitudes or waveforms. The module also generates a picking output file (for tomography) that lists the computed first-break times for each source-receiver pair. Multi-threaded execution is supported for large models.
The input layer velocity model, provided as a GLayerVectorItem. Each layer in this vector defines the geometry (depth, dip, shape) and velocity of one reflector horizon. Connect the output of a layer creation or velocity model import module here. The model must extend over the full spatial range covered by the grid parameters (ModelPointsX, ModelAddPointsX, DX) or the module will report a range error.
The horizontal spacing between model grid points along the X axis, in metres. This is the inline receiver interval. A smaller value gives a finer spatial sampling of the reflector geometry but increases computation time.
Default: 50 m.
The horizontal spacing between model grid points along the Y (crossline) axis, in metres. Set to 0 for 2D modelling. For 3D grid modelling, set this to the crossline receiver interval.
Default: 0 m.
The number of model grid points (receivers) along the inline (X) direction. The total inline extent of the model is ModelPointsX × DX metres. Together with the number of additional grid points, this defines the total spatial extent of the synthetic survey.
Default: 300.
The number of model grid points in the crossline (Y) direction. Set to 1 for 2D modelling. For 3D grid modelling, set this to the number of crossline receiver positions.
Default: 1.
Extra grid points added symmetrically at both ends of the inline axis, beyond the main grid. These extension points ensure that sources near the edges of the survey area can illuminate receivers at the far end of the spread. The input layer model must extend to cover the full range including these additional points: total inline coverage = (ModelPointsX + 2 × ModelAddPointsX) × DX.
Default: 200.
Extra grid points added beyond the crossline axis extents, analogous to the X-axis additional points. Set to 0 for 2D modelling.
Default: 0.
The maximum horizontal aperture (in metres) within which reflections are computed for each source-receiver pair. Only reflector segments within this lateral distance from the specular reflection point contribute to the computed travel times. Setting a smaller aperture speeds up computation; setting a larger aperture is needed for steeply dipping or laterally varying reflectors.
Default: 150 m.
The number of receivers per shot gather (the spread length in grid points). This defines how many receiver positions are active for each source position. Together with the receiver step, this controls the maximum source-to-receiver offset in the synthetic data.
Default: 1.
The index of the first source position in the model grid, numbered from 1. The modelling begins at this source point.
Default: 1.
The index of the last source position in the model grid. Travel times will be computed for all source positions from Number of the first source to this value, stepping by Source step. Set this equal to Number of the grid points (X axis) to model the full inline extent of the survey.
Default: 300.
The increment between consecutive source positions in grid-point units. A value of 1 means every grid point has a source. A value of 2 means every second grid point is a source position, equivalent to a source interval of 2 × DX metres.
Default: 1.
The increment between consecutive receiver positions in grid-point units, analogous to Source step. A value of 1 means receivers are placed at every grid point. This parameter controls the effective receiver interval (Receiver step × DX metres).
Default: 1.
The minimum source-receiver separation in grid-point units. Receiver positions that are closer to the source than this value are excluded from the gather. Set to 0 to include all receivers from zero offset. Increase this value to exclude near-offset traces that may be contaminated by direct wave or ground roll energy in the kinematic model.
Default: 0.
The full path and file name for the output picking text file (with .txt extension). This file contains the computed first-break arrival times for each source-receiver pair in a format compatible with the tomography input modules. Provide this path to save the modelled picking for use in refraction statics or tomo statics workflows that require synthetic first breaks as a starting model.