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<< Click to Display Table of Contents >> Navigation: Stack > Stack imaging (obsolete) |
Stack imaging is an interactive velocity analysis and stacking module. It displays NMO-corrected CDP gathers alongside semblance panels, allows manual and semi-automatic velocity picking, applies muting, and produces stacked inline and crossline sections in real time. The user navigates between analysis locations using a grid of selectable bin positions, edits a velocity function at each bin, and monitors the resulting stack quality interactively.
This module is marked obsolete. For current velocity analysis and stacking workflows, use the dedicated velocity analysis and stack modules in the processing sequence. The module remains available for projects that already contain saved velocity and mute pickings from earlier processing runs.
The seismic prestack dataset to be stacked. Connect the output DataItem from the preceding processing stage.
Handle to the SEG-Y file containing the prestack data. Used for random-access reading of individual CDP gathers during interactive analysis.
Trace header table used to locate and sort CDP gathers by bin position, offset, and other geometry attributes.
Optional preprocessed gather input for passing already-loaded gather data directly into the module.
Optional input stack section (inline or crossline) used as a reference or background display during interactive analysis.
Optional crooked-line geometry description. Connect when processing 2D data acquired along a non-straight profile.
Standard bin grid passed through the sequence. Required when using the Min/max offsets masks feature.
Pre-sorted gather index vector. Provides fast random access to CDP gathers by bin position during interactive navigation.
Path to the .kdb precompute cache file. When the Precompute custom action has been run, the module loads stacked sections from this file instead of computing them on the fly, making interactive navigation much faster. Leave empty to disable precompute.
Path to the saved velocity picking file. Use Load velocity picking and Save velocity picking custom actions to manage this file across sessions. The picking file stores the velocity function at each analysis bin.
Path to the saved mute picking file. Defines the offset-time mute boundary applied before stacking to suppress NMO stretch artefacts and other noise.
Optional separate bin grid input for the offset masking feature. When Min/max offsets masks are enabled, this bin grid provides per-bin minimum and maximum offset limits used to exclude traces outside the valid offset range from the stack.
Optional VRMS velocity model imported from an external source. Connect when Velocity usage is set to External to apply NMO using a pre-existing velocity field rather than the interactively picked velocities.
Mute picking data item passed through the sequence. Contains the mute boundary curves used by the stacking step.
Optional velocity picking item from an upstream module. Connect to initialise the velocity field from a previously run velocity analysis before starting interactive editing.
Inline number (or CDP number for 2D) of the currently selected analysis location. This value updates automatically as you click on bins in the map view or step through the grid using the navigation custom actions.
Crossline number of the currently selected analysis location. For 2D data this field is not used. Updates automatically with bin selection.
Constant velocity (m/s) used as a replacement or initial stacking velocity. This value is applied when no picking exists at a bin and is also used as the reference velocity for residual velocity deviation calculations in the auto-picker. Set to a representative average velocity for the survey area.
Selects the velocity source for NMO correction. Internal (default) uses the velocity function picked interactively within this module. External applies the velocity field connected via the External velocity model input item.
Container grouping general stacking control parameters.
Amplitude threshold for trace inclusion in the stack. Traces whose absolute amplitude exceeds this value at any sample within the stack window are excluded. Default: no limit (FLT_MAX). Reduce this value to suppress high-amplitude noise bursts or spikes before stacking.
When enabled, the module automatically re-stacks bins where the velocity or mute picking has been modified since the last stack update. Default: off. Enable this option to keep the displayed stack section consistent with the current picking without manually triggering a recompute.
Container grouping controls for writing the stack, velocity, and NMO-corrected gather outputs to disk.
When enabled, the stacked inline section is written to the output SEG-Y file during batch execution. Default: off.
When enabled, the velocity gather (semblance panel with velocity picks) inline is written to the output file. Default: off.
When enabled, NMO-corrected CDP gathers are written to the output file during execution. Default: off.
Controls how data is written to the output file. Direct (default) overwrites the output file from the beginning. Append adds the exported data to the end of an existing file, useful for incremental exports of different line segments.
Number of traces read from disk in a single I/O batch during export. Default: 100 traces. Increase this value to improve export throughput on fast storage systems; decrease it if memory is limited.
Container grouping mute application settings.
Length (s) of the cosine taper applied at the mute boundary to avoid abrupt amplitude transitions. Default: 0.064 s. A taper of 0.032–0.128 s is typical. Increase for smoother mute transitions on data with strong coherent noise near the mute boundary.
Container grouping per-bin offset masking parameters. These options require the optional bin grid input to be connected.
When enabled, traces with offsets below the per-bin minimum offset stored in the bin grid are excluded from the stack. Default: off. Use to remove near-offset traces that degrade stack quality due to guided waves or shallow noise.
When enabled, traces with offsets beyond the per-bin maximum offset stored in the bin grid are excluded from the stack. Default: off. Use to limit stack contribution to offsets within the reliable illumination cone for each bin.
Smoothing radius (in bins) applied to the min/max offset mask matrices before use. Default: 0 (no smoothing). Increase to reduce sharp lateral transitions in the offset mask, which can create artefacts in the stack.
Container defining the spacing of the velocity analysis grid. Velocity picking is performed at a subset of CDP bins defined by this grid, and the picks are interpolated to all bins for NMO and stacking.
Step between velocity analysis locations in the inline (or CDP for 2D) direction. Default: 25. A smaller increment provides denser velocity control but requires more picking effort. Choose a value that captures the expected lateral velocity variation.
Step between velocity analysis locations in the crossline direction. Default: 25. For 2D data this field is not used.
Container grouping parameters that control the semblance computation and NMO display.
Minimum velocity (m/s) tested in the semblance panel. Default: 1000 m/s. Set to the lowest plausible stacking velocity for your survey; typically 1400–1500 m/s for marine data or lower for shallow land surveys.
Maximum velocity (m/s) tested in the semblance panel. Default: 6000 m/s. Set to exceed the highest expected interval velocity in your target depth range.
Velocity step (m/s) between tested velocities in the semblance scan. Default: 50 m/s. Finer increments improve picking resolution but increase computation time. Values of 25–100 m/s are typical.
Length (s) of the smoothing window applied to the semblance panel in the time direction. Default: 0.05 s. Increasing this value produces a smoother semblance display that is easier to pick on noisy data, at the cost of slightly reduced time resolution.
Maximum NMO stretch expressed as a fraction. Default: 0.5 (50%). Traces where NMO stretch exceeds this threshold are muted automatically to remove low-frequency NMO stretch artefacts from the stack. Values of 0.3–0.6 are common.
Number of velocity samples used for smoothing the displayed velocity curve in the vertical (time) direction. Default: 10 samples. Increase to suppress pick noise when velocity picks are erratic; decrease for sharper velocity gradients.
Length (s) of the running-window normalization applied to the gather before semblance computation. Default: 0.1 s. This amplitude equalization makes deep and shallow reflections equally visible in the semblance panel. Reduce for a purely amplitude-weighted semblance.
Controls the computational quality of the semblance calculation. Low (default) provides the fastest interactive response. High produces the most accurate semblance panels at the cost of longer computation time per gather. Use High for final quality-control checks.
When enabled, a super gather (stack of neighbouring CDP gathers) and common-offset (CO) gathers are displayed alongside the standard CDP gather and semblance panel. Default: off. Enabling this option activates the Super gather radius and Show CO gathers parameters below. Super gathers improve semblance resolution on data with low fold.
Number of neighbouring bins included in the super gather in the inline direction on each side of the central bin. Default: 3. A radius of 3 combines 7 bins in each direction. Active only when Show NMO super gather and CO is enabled.
Number of neighbouring bins included in the super gather in the crossline direction on each side of the central bin. Default: 3. Active only when Show NMO super gather and CO is enabled.
Controls how common-offset gathers are assembled when super gather display is active. CO with constant step (default) bins traces into regular offset classes defined by the CO radius parameter. CO with original geometry uses the actual offset values from the trace headers without re-binning.
Offset bin half-width (m) used when assembling common-offset gathers with a constant step. Default: 0 m. Set to half the desired CO bin width, for example 50 m for 100 m offset bins. Active only when Show CO gathers is set to CO with constant step.
Container grouping parameters for the residual velocity auto-picker. The auto-picker propagates an initial velocity pick to neighbouring bins by searching for the semblance maximum within a constrained deviation window.
Enables the semi-automatic velocity picker. When active, the auto-picker searches for the semblance maximum nearest to the seed pick location within the deviation bounds defined below. Default: off.
Minimum allowed velocity deviation from the reference pick expressed as a fraction. Default: 0.05 (5%). The auto-picker will not accept a pick that deviates less than this fraction from the seed velocity, preventing it from locking onto noise peaks very close to the reference.
Maximum allowed velocity deviation from the reference pick expressed as a fraction. Default: 0.10 (10%). The auto-picker rejects any semblance peak outside this window, limiting how far the picked velocity can jump between neighbouring bins.
Maximum allowed time deviation of the semblance peak from the seed pick time. Default: 0.01 s. The auto-picker rejects peaks that appear at a time more than this value away from the reference time, preventing misties across the velocity picking grid.
Inline (or CDP) number of the seed bin from which the all-data auto-pick propagation starts. Default: 0. Set to the inline number of the bin where you have made a reliable manual pick.
Crossline number of the seed bin from which the all-data auto-pick propagation starts. Default: 0.
Step between auto-pick locations in the inline direction. Default: 25. This is typically set to match the Inline/cdp increment in the Net params so that the auto-picker covers exactly the velocity analysis grid.
Step between auto-pick locations in the crossline direction. Default: 25.
Maximum number of semblance peaks the auto-picker evaluates per gather. Default: 50. Increase this value if the auto-picker misses picks on complex multi-reflector data; decrease it to speed up processing on simple geology.
Minimum semblance amplitude ratio required for a peak to be accepted by the auto-picker. Default: 1.1. A higher value makes the picker more selective, accepting only well-focused semblance maxima. Reduce toward 1.0 on noisy data where semblance contrast is low.
Container grouping parameters for the mini-stack display. Mini-stacks are partial stacks computed over narrow offset or velocity ranges and displayed in the gather view to aid residual velocity analysis.
When enabled, the sub-sequence processing chain attached to this module is applied to the gather before mini-stack computation. Enable to test the effect of additional processing steps (such as deconvolution or filtering) on the stacked result.
Enables generation and display of mini-stack panels. When off, the mini-stack output gather is not computed, saving processing time during interactive velocity analysis.
Number of neighbouring CDPs included on each side of the central bin when building each mini-stack trace. A larger radius increases fold and reduces noise in each mini-stack column.
Specifies the direction in which the mini-stack traces are assembled. Inline stacks bins along the inline axis; Crossline stacks bins along the crossline axis.
Selects how NMO velocity is applied for the mini-stack columns. Constant velocity stacks produces a panel of stacks at evenly spaced velocities around the current pick, similar to a CVS display. Current interpolated velocity uses the picked velocity function, producing a residual NMO analysis panel.
Velocity step (m/s) between mini-stack columns when using the Constant velocity stacks method. A smaller step produces finer velocity discrimination in the mini-stack panel.
Maximum velocity deviation (m/s) from the current pick that the mini-stack panel spans. This defines the half-width of the velocity range displayed in the mini-stack, centred on the current pick velocity.
Velocity step (m/s) between residual NMO deviation values displayed in the mini-stack panel when using the Current interpolated velocity method.
When enabled, data items are connected automatically when the module is added to the sequence. Disable to configure connections manually.
SEG-Y read cache configuration. Controls the in-memory trace cache used for fast random access during interactive analysis. Adjust the cache size if memory usage is too high or if navigation response is slow.
Selects whether the semblance and NMO computations run on the CPU or a GPU. Select GPU on workstations equipped with a supported graphics card to accelerate interactive semblance calculation.
Configuration for distributed (cluster) execution. When the batch export is run on a compute cluster, these settings control node assignment and job scheduling.
Minimum number of gathers sent to each processing node in a single chunk during distributed execution.
When enabled, limits the number of CPU threads used per cluster node during distributed execution to the value specified in the Number of threads parameter.
Optional text appended to the distributed job name. Use to distinguish simultaneous jobs of the same type running on the cluster.
When enabled, the CPU core affinity for this module is set explicitly using the Affinity mask below. Useful for optimising performance on NUMA (non-uniform memory access) systems.
CPU affinity mask applied when Set custom affinity is enabled. Specifies which CPU cores this module may use.
Maximum number of CPU threads used by this module during batch execution. Higher thread counts increase throughput on multi-core workstations.
When enabled, this module is bypassed during sequence execution and data passes through unchanged. Use to temporarily disable the module without removing it from the sequence.
The NMO-corrected and stacked trace dataset passed to the next module in the sequence.
SEG-Y file handle for the output dataset. Connect to downstream modules that need random read access to the output traces.
Updated trace header table for the output dataset.
The current NMO gather for the selected bin, available for downstream display or analysis modules.
The stacked section (inline or crossline) produced by the module, available for display or further processing.
Updated crooked-line geometry descriptor passed to downstream modules.
Bin grid passed through to downstream modules unchanged.
Sorted gather index vector passed to downstream modules for continued random access.
The final velocity field produced by interactive picking, available for connection to downstream NMO correction, depth conversion, or velocity model building modules.
Container grouping the inline stack and velocity inline output gathers.
The stacked section along the current inline, updated dynamically as you navigate and pick velocities.
The semblance/velocity spectrum panel along the current inline, used to assess velocity picking quality across the line.
Container grouping the crossline stack and velocity crossline output gathers.
The stacked section along the current crossline, updated dynamically as you navigate and pick velocities.
The semblance/velocity spectrum panel along the current crossline.
The mini-stack panel for the currently selected bin, showing partial stacks at varying velocities or residual NMO values. Displayed alongside the CDP gather to help pick the correct stacking velocity.
Computes and stores all stacked sections and velocity panels for the entire dataset in the precompute storage file. Running this action before interactive analysis eliminates computation delay during navigation. This can take significant time on large datasets but greatly speeds up the interactive session afterwards.
Deletes the precompute storage file and resets the module to compute-on-demand mode. Use after changing parameters that invalidate the cached results.
Removes all mute picks for the current session. Use with caution as this cannot be undone once saved.
Loads a previously saved mute picking file from the path specified in the Mute picking input field. Use to restore mute picks from a previous session or import picks from another project.
Saves the current mute picks to the file specified in the Mute picking field. Run this action after completing mute picking to preserve the results.
Removes all velocity picks for the current session.
Loads a previously saved velocity picking file from the path specified in the Velocity picking input field.
Saves the current velocity function picks to the file specified in the Velocity picking field. Run this regularly during interactive sessions to preserve progress.
Runs the semi-automatic residual velocity picker for the currently displayed bin only. The keyboard shortcut Alt+A provides rapid application during interactive navigation. The picker updates the velocity function at the current bin without affecting other locations.
Propagates the velocity picking from the seed bin (defined by the AutoPicker start parameters) to all bins in the velocity analysis grid using the semi-automatic picker. Use after manually picking the seed location to populate the entire survey quickly.
Exports the NMO-corrected gathers, stacked sections, and velocity panels to the output file according to the Export parameters settings. Run after completing velocity picking to write the final results.
Moves the display to the previous analysis location in the inline direction (keyboard: Ctrl+Down). Equivalent to stepping backwards along the inline axis of the velocity analysis grid.
Moves the display to the next analysis location in the inline direction (keyboard: Ctrl+Up).
Moves the display to the previous analysis location in the crossline direction (keyboard: Ctrl+Left).
Moves the display to the next analysis location in the crossline direction (keyboard: Ctrl+Right).