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RefBasedStat (Reflection-Based Statics) is an interactive module for computing and applying surface-consistent static corrections derived from reflection events on seismic CMP gathers. Unlike first-break refraction statics, this method uses reflections from sub-surface horizons, making it effective in areas where the refracted headwave is weak or absent, and for long-wavelength residual statics problems.
The module displays source and receiver gathers alongside a semblance velocity panel. The user picks horizon times manually (or uses the automatic picker), and the module derives source and receiver static shifts from the observed time discrepancies relative to a reference model. It also supports horizontal velocity analysis for near-surface characterisation and interpolation of static corrections between horizons. Use this module in the processing sequence after NMO correction to resolve residual statics that degrade stack quality.
Handle to the input pre-stack seismic data in SEG-Y format. The data should already have NMO correction applied so that reflection events are flattened before picks are made.
Trace header vector containing source/receiver coordinates and CMP numbers used to sort data into source and receiver gathers for the statics analysis.
Input RMS velocity model used for NMO correction during the semblance analysis and for velocity-based interpolation of horizon picks between CMPs.
Optional mute function applied to the input gathers before statics analysis. Muting suppresses direct arrivals and refracted waves that would otherwise corrupt the semblance and reflection picks.
Parameter group for controlling interpolation of static values between horizontally analysed locations and the full data grid.
Name of the active horizon being edited. Select the target horizon from the list before making or modifying picks. All subsequent picking and analysis operations apply to this horizon.
Near-surface replacement velocity in m/s (default: 0 m/s, meaning not applied). This velocity is used to compute the time correction needed to bring data from the acquisition surface to the datum level. Set this to the velocity used in the static corrections applied to the data.
Reference datum elevation in metres (default: 0 m). Static corrections shift traces relative to this datum. Set this to the processing datum used throughout the project.
When enabled (default), the horizontal velocity semblance panel is recalculated each time the selected horizon or display parameters change. Disable this if you want to work with static semblance displays and avoid the overhead of repeated recalculation on large datasets.
Time half-window in seconds (default: 0.2 s) around the horizon pick used when converting from horizontal velocity (HV) analysis to vertical velocity (VV) semblance. Larger windows smooth the result over more of the reflection event.
Lateral smoothing half-window in metres (default: 100 m) for the HV-to-VV conversion. Increasing this value reduces spatial variability in the converted velocity but may smear lateral velocity contrasts.
When enabled, static corrections are interpolated between picked horizons rather than held constant between them. Enable this when multiple horizons are available and you want a smoothly varying statics field with depth.
Parameter group for the horizontal (inline) velocity analysis used to characterise apparent near-surface velocities along the acquisition direction.
Number of traces included in the horizontal semblance stack window (default: 10). Larger values increase the semblance S/N ratio but reduce spatial resolution of the velocity analysis.
When enabled (default), the horizontal semblance display is normalised to equalise amplitude differences between shallow and deep events, making picking more consistent across the full time range.
Parameter group controlling interactive manual horizon picking behaviour.
Time half-window in milliseconds around each mouse click used to search for the optimal pick position (nearest peak, trough, or zero crossing) during manual picking.
Time half-window in milliseconds used by the automatic picker when snapping picks to the nearest event. A narrower window gives more precise but potentially noisier picks; a wider window is more robust but may snap to the wrong event.
The phase component to pick: positive peak, negative peak, or zero crossing. Match this to the polarity convention and waveform phase of the target reflection event.
Minimum amplitude threshold for accepting a manual pick. Picks on samples below this amplitude are rejected, preventing picks on noise. Set this relative to the expected signal amplitude at the target horizon.
Controls how the pick snaps to the nearest event during manual picking. Nearest snaps to the nearest sample of the correct type (peak, trough, or zero crossing). Max energy snaps to the highest-amplitude event within the window.
Parameter group controlling the automatic horizon picking algorithm, used when triggering autopick via the Custom actions.
Search time half-window in milliseconds for the auto-picker. The algorithm searches within this window around the seed pick position to find the highest-quality event on each trace.
Minimum amplitude threshold for the auto-picker. Traces where no event exceeds this value within the search window are left unpicked.
Minimum source-receiver offset in metres used in the auto-picking pass. Traces with offsets below this value are excluded from the automatic picking to avoid near-offset noise and muted zones.
Maximum source-receiver offset in metres used in the auto-picking pass. Traces beyond this offset are excluded to avoid far-offset stretch artefacts.
Snap criterion used by the auto-picker within the search window (Nearest or Max energy). Same semantics as the manual Magnet type parameter.
When enabled, the auto-picker applies a linear regression correction to refine picks after the initial pass, reducing scatter and improving consistency across the gather.
Number of regression refinement iterations. More iterations produce smoother picks at the cost of slightly more computation. Typically 2–5 iterations are sufficient.
When enabled (default), after the auto-picking pass the picks are iteratively refined to improve their consistency with the surrounding gathers.
Parameter group defining the velocity scan range and semblance display settings for the velocity spectrum panel.
Minimum RMS velocity in m/s for the semblance scan (default: 1000 m/s). The velocity panel will display coherence from this velocity upward.
Maximum RMS velocity in m/s for the semblance scan (default: 6000 m/s).
Velocity step in m/s between semblance scan panels (default: 50 m/s). Smaller increments give a finer velocity axis but increase computation time. 25–100 m/s is typical for most statics analysis applications.
Time half-window in seconds applied to smooth the semblance spectrum vertically (default: 0.05 s). A wider window produces a smoother semblance panel that is easier to pick, but reduces time resolution.
NMO stretch mute threshold as a fraction (default: 0.5, i.e. 50%) applied during the semblance calculation. Traces where the NMO stretch exceeds this value are excluded from the semblance stack to suppress far-offset noise.
Time window in seconds used to normalise the semblance for display (default: 0.1 s). Normalisation balances the display of shallow high-amplitude events against deeper low-amplitude events.
Quality/resolution trade-off setting for the semblance calculation. High gives the most accurate semblance but is slowest. Low (default) is fastest and sufficient for interactive QC. Use High for final picks on critical horizons.
Lateral radius in metres for the super-gather stack used to improve semblance S/N (default: 75 m). Neighbouring CMPs within this radius are stacked before computing the semblance, boosting signal coherence on noisy data. Set to 0 to disable super-gather stacking.
Parameter group for NMO velocity analysis settings.
Number of samples used for vertical (time axis) smoothing of the velocity field (default: 10 samples). Larger values produce a smoother velocity model that is less sensitive to individual pick errors.
Parameter group for importing horizons from external ASCII files using the Import horizon ASCII custom action.
Reference surface for the horizon times in the import file. Datum means times are referenced to the processing datum. Topography means times are measured from the surface elevation.
Datum elevation in metres used as the reference level when Location is set to Datum (default: 0 m).
Time units in the import file: Milliseconds (default) or Seconds. Ensure this matches the units in the ASCII file being imported.
Parameter group controlling the spatial interpolation of imported horizon times onto the processing grid.
Grid interpolation step in the X direction in metres (default: 200 m). The imported horizon is re-sampled onto a regular grid at this spacing before being mapped to CMPs.
Grid interpolation step in the Y direction in metres (default: 200 m).
Removes all current mute picks, resetting the mute function to an empty state.
Loads a previously saved mute function from file and applies it to the input data for this session.
Saves the current mute function to file for re-use in other modules or sessions.
Computes and writes a CMP stack using the current velocity model and static corrections. Use this to evaluate the quality of the statics solution.
Exports the current picked RMS velocity model as an output VRMS item for use in downstream NMO correction or depth conversion modules.
Imports horizon times from an ASCII file into the current horizon layer using the settings defined in the Import horizons from ASCII params group.
Exports the currently selected horizon picks to an ASCII text file for use in external applications or for archiving.
Saves all horizon picks in native binary format for fast reload. Use this to checkpoint work in progress.
Restores horizon picks from a previously saved binary file.
Converts horizon picks made on time-amplitude (TA) gathers into source-domain static picks, enabling the static decomposition step.
Converts horizon picks made on time-amplitude gathers into receiver-domain static picks for decomposition.