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The Statics - Reflection Based module computes residual static corrections by cross-correlating NMO-corrected traces within a supergather. For each CDP location, the module assembles a supergather from all CMPs within a configurable radius, applies NMO correction using the connected Vrms model, and then cross-correlates each trace against the supergather pilot stack. The resulting time shifts are decomposed into per-shot and per-receiver components (surface-consistent decomposition), which are then applied as static corrections to flatten the gathers. This process implements the PACS (Pilot-Aided Cross-correlation Statics) and SAE (Stack Amplitude Enhancement) reflection statics methodology.
The module supports multiple supergather passes (controlled by the radius iteration parameters), progressively expanding the supergather radius to refine the static solution. An optional slope correction mode allows picks along interpreted horizons to constrain the statics solution, improving performance in areas with complex near-surface conditions. Input azimuthal statics from a previous step can optionally be loaded to provide a starting model for the correction. Multi-threaded execution is supported for production processing of large datasets.
The primary seismic data stream. For this module, data is read directly from a SEG-Y file via the SEG-Y handle input rather than streamed gather-by-gather; this input is used for data routing within the workflow.
The handle to the SEG-Y file containing all input traces. The module reads traces in random-access order (by CDP) to assemble supergathers, so the entire dataset must be accessible through this handle. Connect the output of an Open SEG-Y or Save SEG-Y module here.
The trace header collection providing geometry information (source and receiver numbers, CDP numbers, offsets) for all traces in the input dataset. The module uses these headers to identify which traces belong to each supergather and to map the computed shifts back to individual shots and receivers for the surface-consistent decomposition.
The root-mean-square velocity model used to apply NMO correction before cross-correlation. Accurate NMO correction is essential for the cross-correlation to measure residual statics rather than primary moveout. Connect the output of your velocity analysis module here. The model must cover the full time range defined by the Window up and Window down parameters.
An optional input containing previously computed azimuthal or surface-consistent static corrections to be used as a starting model. When connected, the module adds the newly computed residual statics on top of these input corrections, allowing an iterative workflow where each pass refines the statics solution. Leave this input unconnected to compute statics from scratch.
The start time (top) of the correlation window in seconds, measured as two-way time from the surface. Only the portion of each NMO-corrected trace between Window up and Window down is used for cross-correlation. Set this to a time just below the mute zone, above the shallowest reliable reflection event you wish to use for the statics computation.
Default: 0.5 s.
The end time (bottom) of the correlation window in seconds. Including deeper, high-quality reflectors in the correlation window generally produces more robust statics estimates by averaging over more events. Avoid including multiples or poor-quality deep events that could bias the cross-correlation.
Default: 2.0 s.
The first CDP bin number to process. Use this parameter to restrict the statics computation to a specific range of CDPs, for example to process only a sub-line or to reprocess a problem area. Set both Start bin and End bin to 0 to process all CDPs in the dataset.
Default: 0 (process all CDPs).
The last CDP bin number to process. Set to 0 (together with Start bin = 0) to process the entire dataset. When set to a non-zero value, only CDPs from Start bin through End bin inclusive are processed.
Default: 0 (process all CDPs).
The maximum allowable time shift in seconds for any single cross-correlation measurement. The cross-correlation is searched only within ±Maximum static shift relative to zero lag, and the peak within that range is taken as the measured static. Set this to be slightly larger than the expected maximum residual static in your dataset. Values larger than necessary may cause the correlation to lock onto multiple events rather than the correct peak; values too small may clip genuine statics at the edges.
Default: 0.02 s (20 ms).
The minimum normalised cross-correlation coefficient required to accept a static shift measurement. Measurements with a peak correlation below this threshold are rejected and not used in the surface-consistent decomposition. Set a higher threshold (e.g. 0.3–0.5) to include only high-confidence measurements and reduce the influence of noisy traces; set to 0.0 to accept all measurements regardless of quality.
Default: 0.0 (accept all measurements).
When enabled, the NMO correction is not applied before cross-correlation, and the traces are correlated in their original (NMO-uncorrected) form. This option can be useful for post-stack data or when the input data has already been NMO-corrected elsewhere in the workflow and applying NMO again would distort the data. By default (disabled), NMO is applied as part of the statics computation.
Default: Disabled (NMO is applied).
This group controls the iterative supergather scheme. In each iteration, the supergather radius is increased by Radius step CDPs from Radius start to Radius end, and the cross-correlation and surface-consistent decomposition are repeated. Starting with a smaller radius uses closely spaced CMPs to capture high-frequency lateral statics variation, while later passes with larger radii provide better statistical averaging for low-frequency trends.
The number of CDPs on each side of the central CDP included in the supergather during the first iteration. A radius of 3 includes 7 CDPs total (the central CDP plus 3 on each side). For densely sampled 3D surveys, a radius of 2–5 CDPs is typical for the first pass.
Default: 3 CDPs.
The supergather radius used in the final iteration, in CDPs. When Radius end equals Radius start, only a single iteration is performed with a fixed radius. Increase Radius end to run additional passes with progressively larger supergathers.
Default: 3 CDPs.
The increment by which the supergather radius is increased between iterations, in CDPs. For example, with Radius start = 2, Radius end = 6, and Radius step = 2, the module performs three iterations using radii of 2, 4, and 6 CDPs.
Default: 1 CDP.
The number of surface-consistent decomposition iterations performed at each supergather radius. More iterations allow the decomposition to converge more closely to the true surface-consistent solution, particularly when the statics are large. For most surveys, 3–5 iterations at each radius are sufficient. Increasing this number improves accuracy at the cost of additional computation time.
Default: 3.
This group provides options for incorporating dipping-event (slope) information into the statics solution. Using slope corrections can improve the statics estimates in areas where the reflectors are not horizontal and the cross-correlation would otherwise measure a combination of dip and static.
Selects the method used to determine the dip (slope) of reflectors for the slope correction. Three options are available:
None — no slope correction is applied. Use this when the reflectors are approximately horizontal or when you do not have reliable dip information.
Auto find slope in window — the module automatically estimates the dominant reflector dip at each location by scanning within the correlation window at the time step specified by Auto horizons step. Use this option when horizon picks are unavailable but significant dip is present.
Horizon picking ext. — uses the horizon picks supplied through the Input horizons input to derive the dip at each CDP location. This is the most accurate option when reliable horizon picks are available.
Default: None.
The time interval, in seconds, at which the automatic dip estimation is performed within the correlation window when Use slopes correction is set to Auto find slope in window. A smaller step estimates dip at finer time intervals but increases computation time. Use a value comparable to the typical reflector spacing in your data.
Default: 0.25 s.
The horizon picking item providing interpreted reflector dips for the slope correction. This input is used only when Use slopes correction is set to Horizon picking ext. Connect the output of a horizon extraction or horizon picking module that covers the same time range as the correlation window.
This group controls the velocity parameters used when applying the computed static corrections to the data, particularly for the NMO stretch mute.
The replacement (datum) velocity used to apply the bulk static shift when converting computed time shifts to equivalent datum corrections, in m/s. This value is typically set to the average velocity of the replacement layer (e.g. the velocity used for weathering corrections) and should be consistent with the replacement velocity used in the statics application step.
Default: 1550 m/s.
The NMO stretch mute threshold applied before cross-correlation, expressed as a fraction (0–1). Samples stretched by more than this fraction of their original duration are excluded from the correlation window. This prevents the highly stretched far-offset shallow samples from dominating the correlation and producing spurious static measurements. A value of 0.25 (25%) is more conservative than the standard 50% mute and produces cleaner correlations at the cost of using fewer offset-time samples near the mute zone.
Default: 0.25 (25%).
The computed surface-consistent static corrections for all shots and receivers, stored as an azimuthal statics correction item. This output can be connected to a static application module to apply the corrections to the gathers, or fed back into the Azimuthal statics correction item - input in a subsequent run for iterative refinement.
Clears all currently computed static shift values from the module's internal storage, resetting the solution to zero. Use this action before rerunning the computation with modified parameters to ensure that no residual shifts from a previous run are carried over.
Computes and displays the residual statics — the difference between the cross-correlation shifts and the current surface-consistent solution. Reviewing the residual allows you to assess the quality of the statics solution and identify areas where the decomposition has not converged. Large residuals indicate that additional iterations or a wider supergather radius may be needed.
Removes the CDP (common mid-point) component from the computed static solution, retaining only the true surface-consistent shot and receiver components. The CDP component represents a long-wavelength datum shift that may not be a genuine static and could distort the final stack. Use this action to clean the solution before applying statics when a significant CDP component is present.
Computes and stores the reflector dip (slope) estimates from the data using the method selected in the Use slopes correction parameter. Run this action before the main statics computation when using slope corrections to pre-calculate the dip table and verify that the dip estimates are geologically reasonable before proceeding.
Clears all stored reflector slope estimates. Use this action to discard a previously computed dip table before recomputing it with updated parameters or a different horizon set.