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Depth angles mute is an interactive, AVO-oriented module that converts pre-stack depth-migrated common-image gathers (CIGs) into common-angle gathers (CAGs) and allows the user to apply selective muting across angle stacks. The module computes, for each CIG trace and depth sample, the corresponding opening angle using the local interval velocity (or VRMS) and offset, then bins traces into user-defined angle ranges to form per-angle depth stacks.
Once the angle stacks are created, the user interactively paints mute masks directly on the displayed angle stack sections using an elliptical eraser tool. Painted regions can be added (left-click + Shift) or removed (right-click), enabling fine control over angle-dependent noise suppression. After masking, the module merges all angle stacks with smooth taper blending to produce a final weighted-average angle stack volume. Masks can be saved to disk and reloaded in future sessions.
Note: This module is deprecated. It is preserved for legacy workflows. New projects should use the current AVO / common-angle gather tools available in g-Platform.
Connect the SEG-Y file handle containing the pre-stack depth-migrated data (CIGs). This is the source of the amplitude data that will be angle-binned and muted.
Connect the trace header vector associated with the input SEG-Y data. The module reads offset values and bin geometry from these headers to compute per-sample angles and to organise traces into the correct spatial bins.
Connect the depth-domain interval velocity gather. The module uses this velocity field to compute the opening angle at each depth sample for every CIG trace using the relationship between offset, two-way time, and interval velocity. The velocity gather must be in the depth domain and cover the full spatial extent of the CIG data. When Alt mode is enabled, an VRMS (root-mean-square velocity) gather is used instead.
A dropdown list that becomes populated after running the Recreate common angle gathers action. Each entry in the list corresponds to one angle bin (for example, 0°, 10°, 20°, ...). Selecting an angle from the list activates that angle stack in the interactive display, allowing you to inspect it and paint the mute mask for that specific angle. The eraser tool and mask editing always act on the currently selected angle.
Near-surface reference velocity, in m/s. Default: 3500 m/s. This velocity is used to handle the portion of the ray path above the datum level and is applied when converting between depth and time in the Alt calculation mode. Set V0 to a representative weathering or near-surface velocity for your survey area. In most hard-rock environments a value of 3000–4000 m/s is appropriate; for soft sediment areas use a lower value.
The sample interval (in seconds) used for intermediate time-domain gathers when the Alt calculation mode is active. Default: 0.004 s (4 ms). The minimum allowed value is 0.00001 s. In standard (non-Alt) mode this parameter has no effect. When using Alt mode, set this to match the sample rate of your input VRMS velocity field or the desired output temporal resolution.
The total recording length (in seconds) for intermediate time-domain gathers in Alt mode. Default: 4 s. The minimum allowed value is 0.004 s. Set this to cover the full two-way travel time range of your data before depth conversion. It has no effect when Alt mode is disabled.
Toggle between two angle-computation methods. Default: off (standard mode). When off, the module computes angles directly in the depth domain using the connected interval velocity field and the offset from trace headers. When on, the module temporarily converts the depth CIG to the time domain, computes angles from a VRMS field, forms the CAG in time, and then converts back to depth. The Alt path also enables a sub-sequence that can apply additional processing between the time-domain CIG and the final CAG. Use Alt mode when a reliable VRMS model is available and results from the standard depth-domain method are unsatisfactory.
This parameter group controls how common-angle gathers are constructed from the input CIGs, including the angle binning geometry, edge blending, and smoothing applied to each angle stack.
Controls the taper length (in depth samples) applied at the lower edge of each angle stack where it transitions to the next angle bin. Default: 12 samples. A linear blend is applied over this many samples at the bottom boundary of the valid data zone in each angle gather, ramping the amplitude from the current angle stack toward the adjacent (lower-angle) stack. Increasing this value produces a gentler, more gradual transition between angle stacks and reduces sharp boundary artefacts. Reducing it to a small number produces a hard boundary between angle stacks.
Controls the taper length (in depth samples) applied just above the lower boundary of the valid data zone in each angle stack — that is, on the opposite side of the boundary from CAG edge smooth. Default: 1 sample. A short ramp is applied here so that the previous angle bin's contribution fades smoothly to zero in the shallow direction. In most cases the default value of 1 is sufficient, but you can increase it if the edge of the illuminated zone shifts rapidly with angle and causes visible banding.
The half-width of the smoothing window applied in the angle dimension when the 3D taper is applied to the mute mask before forming the final stack. Default: 1 angle bin. A value of 1 means the smoothing blends over 3 adjacent angle bins (the target bin and its immediate neighbours on each side). Increase this value when the mute mask boundary is sharp in the angle direction and you want a broader, more gradual fade between muted and unmuted angle zones.
The half-width of the smoothing window applied in the lateral (trace) dimension when the 3D taper is applied to the mute mask. Default: 15 traces. This controls how many neighbouring traces on each side are included in the smoothing of the mask boundary. A larger value produces a spatially smoother transition at painted mute mask edges, which is important for avoiding lateral amplitude discontinuities in the final stack.
The half-width of the smoothing window applied in the vertical (depth sample) dimension when the 3D taper is applied to the mute mask. Default: 15 samples. This governs how many depth samples above and below each painted mask boundary are included in the taper. Increase this value to obtain a gradual amplitude taper in the vertical direction at the edges of muted zones, preventing sharp horizontal amplitude breaks in the output stacks.
The minimum opening angle (in degrees) of the first angle bin. Default: 0°. Traces with computed angles below this value are excluded from all angle stacks. Typically set to 0° to include near-vertical rays. Increase this value to exclude very near-offset illumination if it is contaminated by direct-wave energy or other near-offset noise.
The maximum opening angle (in degrees) of the last angle bin. Default: 90°. Traces with computed angles beyond this value are excluded. In practice, reflection data is rarely reliable beyond 45–60°, so setting this to a geophysically meaningful maximum angle (such as 45°) avoids populating bins that would contain only noise or aliased energy. The total number of angle bins created is determined by (Last angle − First angle) / Step angle, rounded up.
The angular width of each angle bin, in degrees. Default: 10°. Minimum: 0.1°. Smaller step angles produce more angle bins with narrower angular apertures, which gives finer AVO resolution but lower fold per bin (and therefore lower signal-to-noise ratio per stack). Larger step angles give broader bins with higher fold. A typical choice for AVO work is 5°–15° per bin.
The vertical smoothing window length (in seconds) applied to the computed per-sample angle field before binning CIG traces into angle gathers. Default: 0.25 s. Maximum: 5000 s. Smoothing the angle field reduces the effect of rapid velocity fluctuations on the angle computation, producing more stable and geologically reasonable angle assignments. Increase this value when the velocity model is noisy or when you observe unstable trace assignments near the edges of angle bins. Decrease it only if you need to preserve rapid vertical variation in the angle-to-offset mapping.
This parameter group is inherited from the base interpolator and controls spatial interpolation of parameters across the survey area. It defines how the velocity and other spatially varying fields are sampled and interpolated at each bin location. The parameters within this group include the interpolation method (Kriging or Triangulation), covariance type, search radius, and number of neighbouring points used. These settings affect the quality of the velocity interpolation applied when computing angles at each CIG location.
The interactive angle stack with the current mute mask applied. This is the primary display for interactive mask painting. As you paint or erase the mask on this view, the display updates in real time. The muted (zeroed) regions reflect the areas you have marked for suppression. This item is pickable — you can interact with it using the eraser tool directly in the vista panel. Only the currently selected angle (chosen from the Current angle dropdown) is displayed at a time.
The merged output stack produced by the Create stack by angle gathers action. This gather is a weighted-average combination of all angle stacks, where the weight at each sample position is determined by the tapered mute mask. At each sample, only angle bins that are not fully muted contribute to the sum, and the result is normalised by the total mask weight to preserve amplitude balance. This output represents the final deliverable depth-domain stack with angle-selective noise suppression applied.
The reference angle stack without any mute mask applied. This display is available for comparison with the masked version to assess the effect of the muting you have painted. It is also pickable in the vista panel, making it useful as a reference while editing masks. Both the masked and reference angle stacks are shown in the same Angle stack depth vista view alongside the eraser overlay and the final stack.
The module provides three custom actions accessed from the module toolbar or context menu:
Recreate common angle gathers — Reads all CIGs from the input data, computes per-sample opening angles using the depth velocity (or VRMS) field, and bins the data into angle stacks according to the First angle, Last angle, and Step angle settings. The Current angle dropdown is populated with the resulting angle bin labels. Run this action first, before any mask painting. If you change any angle geometry parameters (First angle, Last angle, Step angle), re-run this action to rebuild the gathers.
Create stack by angle gathers — Merges all angle stacks using the current mute masks to produce the Final angle stack output. The mask is first smoothed using the Smooth taper angle, Smooth taper trace, and Smooth taper sample settings, and then used as a per-sample weight. Run this action after you have finished painting all angle masks to generate the output volume.
Clear/Save/Load mask — Opens a dialog with four options: (1) Clear current angle mask — resets the mask for the currently selected angle only, restoring all samples to unmasked; (2) Clear full mask — resets all angle masks simultaneously; (3) Save mask — writes all current masks to a binary .gmask file so they can be re-applied in a later session; (4) Load mask — reads a previously saved .gmask file and applies it to the current angle stacks. If the loaded mask was saved in the time domain (from a previous Alt-mode session), it is automatically converted to depth before application.
Once the angle gathers have been created, open the Angle stack depth vista panel. The Eraser overlay defines an elliptical brush whose position tracks the mouse cursor. To add a mute region, hold Shift + Left-click and drag across the area you want to suppress. To restore a previously muted area, use Right-click and drag. The eraser brush size is determined by the delta of the pointer position as displayed in the vista view. Switch between angle bins using the Current angle dropdown to paint masks on different angle stacks. The Current angle overlay (horizon picks style) shows the angle boundary curve for the selected angle bin on the angle gather display.