Description

Statics - horizon based computes surface-consistent static corrections guided by interpreted horizon picks. Instead of cross-correlating all traces within a broad time window, the algorithm focuses the alignment on specific reflection horizons. For each picked layer the module estimates the two-way time (T0) of the reflector at each CDP bin, optionally refines the velocity model by running a horizontal velocity analysis (HVA) semblance, and cross-correlates traces against a bin-stack model within a narrow window centred on the horizon. The resulting trace shifts are decomposed into surface-consistent source and receiver static corrections using a least-squares solver.

Use this module when well-defined seismic horizons are available and you want to restrict the statics estimation to specific geological reflectors rather than the entire trace. It is particularly effective in areas with strong lateral velocity variation where broadband cross-correlation would produce unreliable shift estimates. Connect the VRMS model and the horizon picking item from the interpretation workflow before running. Use the Update HVA semblance custom action to recompute the velocity analysis panel for the selected bin.

Input data

Input DataItem

The prestack seismic dataset. Connect the output DataItem from the preceding sequence module.

Input SEG-Y data handle

SEG-Y file handle for random-access reading of CDP gathers during interactive bin navigation and batch processing.

Input trace headers

Trace header table providing source, receiver, and CMP geometry for gather assembly and map display.

Input gather

Current CDP gather from the sequence iterator, used for interactive display.

Input stack line

Stack line passed through the sequence.

Input crooked line

Crooked-line geometry descriptor for 2D surveys with non-straight profiles.

Input bin grid

Bin grid passed through the sequence.

Input sorted headers

Sorted gather index vector for fast random-access CDP gather retrieval.

VRMS model

VRMS velocity model used to apply NMO correction before computing semblance panels and cross-correlating traces against the model. Connect the output from a velocity analysis or velocity application module.

Input horizons

Horizon picking item containing the interpreted reflection times for each layer. The module uses these picks to centre the cross-correlation window and velocity analysis at each horizon. Connect from the Extract Horizon or Horizon slice extractor module output.

Parameters

General

Container grouping the datum and replacement velocity parameters applied to correct all traces to a common datum before statics estimation.

Replacement velocity

Near-surface replacement velocity (m/s) used for bulk datum correction applied to all traces before statics estimation. Default: 1550 m/s. Set to the estimated average weathering-zone velocity for your survey area.

Shift to datum

When enabled, a bulk elevation static is applied to shift all traces from their actual surface elevation to the Datum elevation before processing. Default: off. Activates the Datum parameter when turned on.

Datum

Target datum elevation (m) for the bulk static correction. Default: 0 m. Active when Shift to datum is enabled.

Horizon parameters

Container grouping the layer selection and horizon-related settings.

Current layer

Selects the active horizon layer used for velocity analysis and cross-correlation. The list is populated from the connected Input horizons picking item. Select the horizon closest to the depth range where statics correction is most important.

Velocity analysis

Container grouping parameters for the horizontal velocity analysis (HVA) semblance used to refine the velocity at each CDP bin.

Min velocity

Minimum velocity (m/s) tested in the HVA semblance scan. Default: 1000 m/s.

Max velocity

Maximum velocity (m/s) tested in the HVA semblance scan. Default: 6000 m/s.

Step velocity

Velocity step (m/s) between tested velocities. Default: 50 m/s.

Time window

Half-length (s) of the time window used for semblance computation around the horizon pick. Default: 0.05 s.

Use super gather

When enabled, gathers from neighbouring bins within the Super gather aperture are combined into a super gather before semblance computation, increasing fold and improving velocity resolution. Default: off. Activates the Super gather aperture parameter.

Super gather aperture

Spatial radius (m) around each bin from which neighbouring gathers are included in the super gather. Default: 200 m. Active when Use super gather is enabled.

Use normalization

When enabled (default), trace amplitudes are normalised before semblance calculation to equalise shallow and deep reflectors in the velocity panel. Activates the Normalization aperture parameter.

Normalization aperture

Spatial aperture (m) over which amplitudes are normalised. Default: 200 m. Active when Use normalization is enabled.

Stretch factor

NMO stretch mute threshold (fraction) applied before semblance computation. Default: 0 (no mute). Set to 0.3–0.6 to suppress NMO stretch artefacts from far-offset traces.

Velocity smooth time window

Time smoothing window (s) applied to the semblance panel before velocity picking. Default: 0.05 s.

Solver params

Container grouping all parameters that control how trace-level shift measurements are decomposed into per-source and per-receiver static corrections.

Solve by T0

When enabled (default), the horizon pick time T0 at each bin is used as a measurement constraining the surface-consistent decomposition. Activates the Horizon smooth window X/Y parameters. Enable when horizon picks are reliable and well-distributed across the survey.

Horizon smooth window X

Spatial smoothing radius (m) applied to the horizon time surface in the inline direction before using T0 as a constraint. Default: 2000 m. Active when Solve by T0 is enabled.

Horizon smooth window Y

Spatial smoothing radius (m) applied in the crossline direction. Default: 2000 m. Active when Solve by T0 is enabled.

Solve by VRMS

When enabled (default), HVA-derived VRMS velocities are included as constraints in the surface-consistent solver. Activates the VRMS smooth window X/Y parameters.

VRMS smooth window X

Spatial smoothing radius (m) applied to the VRMS velocity field in the inline direction before using it as a constraint. Default: 2000 m. Active when Solve by VRMS is enabled.

VRMS smooth window Y

Spatial smoothing radius (m) in the crossline direction. Default: 2000 m. Active when Solve by VRMS is enabled.

Solve by cross-correlation

When enabled (default), trace-level cross-correlation measurements are included as constraints in the surface-consistent solver. Activates the Cross-correlation window and Cross-correlation max shift parameters.

Cross-correlation window

Length (s) of the time window used for trace cross-correlation, centred on the current horizon pick. Default: 0.3 s. Active when Solve by cross-correlation is enabled. Set to encompass the full reflection wavelet while excluding noise from other horizons.

Cross-correlation max shift

Maximum time shift (s) allowed in the cross-correlation search. Default: 0.03 s. Active when Solve by cross-correlation is enabled. Set to the maximum expected residual static after previous corrections.

Trace static factor

Scaling factor applied to the raw cross-correlation shift measurements before they enter the solver. Default: 1.0 (no scaling). Reduce below 1 to damp the influence of large cross-correlation shifts on the surface-consistent solution.

Solve method { Trace statics only, LSCG, Gauss-Seidel }

Linear solver used to decompose trace shifts into source and receiver components. Trace statics only applies the raw trace shifts without surface-consistent decomposition. LSCG (default) uses a least-squares conjugate gradient solver. Gauss-Seidel is an iterative relaxation solver suitable for sparse or irregular geometry. LSCG is the recommended choice for most datasets.

Number of iterations

Maximum number of conjugate gradient iterations. Default: 100. The solver stops early when the residual drops below Epsilon. Increase only if convergence is not achieved at 100 iterations.

Epsilon

Convergence tolerance for the linear solver. Default: 1e-6. The solver stops when the relative residual norm falls below this value. Decrease for higher accuracy at the cost of more iterations.

Use picket consistent solver

When enabled, the solver enforces a smooth variation of static corrections along source or receiver lines (pickets) using a Tikhonov regularisation term. Default: off. Activates the Picket consistent solver variable step and Lambda parameters when enabled. Use on land data where source or receiver inline static variation should be smooth.

Picket consistent solver variable step

Spatial step (m) between stations along the line used in the picket-consistent constraint. Default: 1000 m. Active when Use picket consistent solver is enabled.

Lambda

Regularisation weight for the Tikhonov smoothness constraint. Default: 1.0. Larger values enforce stronger spatial smoothing of the static corrections. Active when Use picket consistent solver is enabled.

Use structure term

When enabled, a structural (CMP) term is added to the decomposition to absorb residual NMO or dip contributions. Default: off. Use with caution as this term can absorb genuine long-wavelength near-surface anomalies.

Use offset term

When enabled, an offset-dependent term is added to the decomposition to account for residual moveout between offset classes. Default: off.

Apply offset weights to equations

When enabled, each cross-correlation measurement is weighted inversely by its offset before entering the least-squares system, giving greater weight to near-offset traces which typically have higher signal-to-noise ratio. Default: off. Activates the Offset power parameter.

Offset power

Exponent applied to the inverse offset weighting. Default: 1.0. A value of 1 gives linear inverse-offset weighting; higher values increase the relative weight of near-offset traces more aggressively. Active when Apply offset weights to equations is enabled.

Settings

Auto-connection

When enabled, data items are connected automatically when the module is added to the sequence.

SegyReadParams

SEG-Y read configuration. Adjust trace reading parameters to match the SEG-Y byte convention of the input file.

Execute on { CPU, GPU }

Selects CPU or GPU execution for semblance and cross-correlation computations.

Distributed execution

Cluster execution configuration for distributed processing.

Bulk size

Minimum gather chunk per compute node during distributed execution.

Limit number of threads on nodes

When enabled, limits the CPU thread count per cluster node.

Job suffix

Optional text appended to the cluster job name.

Set custom affinity

When enabled, sets the CPU affinity mask for this module explicitly.

Affinity

CPU affinity mask when Set custom affinity is enabled.

Number of threads

Maximum CPU thread count used during execution.

Skip

When enabled, bypasses this module during sequence execution.

Output data

Statics correction item

The computed surface-consistent static corrections for all sources and receivers. Connect to a downstream statics application module.

Selected bin gather

Raw CDP gather for the currently selected bin, displayed for QC of gather alignment.

Selected bin gather NMO

NMO-corrected CDP gather for the selected bin, used to assess velocity quality at the selected horizon.

Selected bin gather NMO

CDP gather sorted by source for the selected bin, providing a complementary view of static consistency across sources.

Selected bin gather NMO

NMO-corrected CDP gather sorted by source for the selected bin.

VRMS inline

Updated VRMS velocity panel along the current inline, showing the HVA-derived velocity picks and the smoothed horizon surfaces used for statics estimation.

VRMS crossline

Updated VRMS velocity panel along the current crossline.

Information

Graphics

Custom actions

Update HVA semblance

Recomputes the horizontal velocity analysis semblance panel for the currently selected bin. Use this action to refresh the HVA display after changing velocity analysis parameters or after picking a different horizon layer. The semblance panel is shown in the HVA semblance view panel and is used interactively to verify or edit the velocity at each horizon pick location.