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<< Click to Display Table of Contents >> Navigation: MultiFocusing > MF Fold 3D |
The MF Fold 3D module creates a spatially varying Fresnel Zone (FZ) factor map and calculates the nominal Multi-Focusing (MF) fold for a 3D survey. For each bin in the computation area, the module scans a range of FZ factor values and determines which factor achieves a target (Desired MF Fold) stacking fold. When the desired fold cannot be reached, the maximum FZ factor is used. The resulting FZ factor map can be supplied to the MF search engine to adaptively expand the stacking aperture in sparsely covered areas, improving MF image quality in regions with irregular acquisition fold.
Use this module when your survey has strongly irregular fold due to overlapping acquisitions with different parameters, obstacles, or marine turns. The adaptive FZ factor map produced here prevents over-smoothing in well-sampled areas and under-sampling in poorly-sampled areas during the MF search.
Link to the trace header vector containing source and receiver positions for the full 3D dataset. The module uses these headers to count how many traces contribute to each bin at each FZ factor level.
Link to the BinGrid item defining the 3D survey inline/crossline geometry. This bin grid determines which bin each trace belongs to and sets the spatial extent of the FZ factor map.
Link to the MF parametrization item (created by the MF Engine Parametrization module) defining the offset and azimuth quantization tables used by the Multi-Focusing search. The base Fresnel Zone size is taken from this parametrization and scaled by the FZ factor computed here.
Container group controlling the Fresnel Zone factor scanning and the desired fold target. The module scans FZ factor values from Min FZ factor to Max FZ factor in steps of Step fz factor and selects the smallest factor that achieves the Desired MF Fold at each bin location.
Maximum Fresnel Zone scale factor permitted during the scanning. Default: 1. The scanning stops at this value even if the Desired MF Fold has not been reached; the maximum factor is then assigned to that bin. Increase this value in surveys with large gaps in acquisition coverage where a wider stacking aperture is needed to achieve the target fold.
Target number of traces that should contribute to each bin's MF stack. Default: 0. When set to 0, the module computes the nominal MF fold using the base Fresnel Zone defined in the MF parametrization, without adaptive scaling. When set to a positive value, the module expands the FZ factor at each bin location until this fold target is reached or the Max FZ factor is exhausted. Set this to the minimum acceptable fold for reliable MF imaging in your survey.
Minimum acceptable MF fold. Bins whose fold remains below this threshold after applying the maximum FZ factor will have their stacking aperture reduced to zero (effectively excluded from the MF image). Default: 0 (no exclusion). Set this to a non-zero value to mask out bins with insufficient coverage and prevent them from contaminating the final MF image.
Number of CPU threads used for parallel fold computation. Set to the number of available physical cores for best performance.
Matrix item containing the computed MF fold map — the number of traces contributing to each bin at the selected FZ factor. Connect this to the MF search engine to weight the stacking aperture spatially.
Matrix item containing the spatially varying Fresnel Zone factor map — the scale factor assigned to each bin location to achieve the desired MF fold. Connect this to the MF search engine so that it applies the adaptive FZ size during imaging.
Refreshes the displayed calculation area polygon based on the current inline and crossline range settings. Use this after changing the calculation area limits to confirm the area is set correctly before running the full fold computation.