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Transforms a prestack NMO-corrected gather into a set of common-angle stacks. For each defined angle bin, the module identifies all traces whose reflection angle falls within that bin at each time sample and averages their amplitudes to produce one output trace per bin. This workflow is fundamental to AVO (Amplitude Versus Offset) analysis, where separating the seismic response by incidence angle reveals information about subsurface rock and fluid properties.
Two input gathers are required: the NMO-corrected amplitude gather and a companion gather containing the reflection angle for every trace and time sample. The output trace offset header is set to the centre angle of each bin.
The NMO-corrected prestack gather containing the seismic amplitudes to be stacked. NMO correction must be applied beforehand so that reflection events are flattened across the gather. Dimensions must exactly match the Input gather Angles.
A gather of the same dimensions as the NMO gather in which each sample value is the reflection incidence angle in degrees for the corresponding trace and time sample. Typically produced by an angle computation module using offset and velocity information. The angle values are smoothed internally by the Angle smooth window length parameter before bin assignment.
The starting incidence angle of the first output angle sub-stack, in degrees. Traces with a computed angle at or below this value are excluded. Default: 0°. Set to a small positive value (2–5°) to exclude near-vertical reflections dominated by noise.
The upper limit of the angle range, in degrees. Traces with angles at or above this value are excluded. Default: 15°. For AVO analysis this is typically set in the range 30–45°, which is the practical limit beyond which NMO stretch and amplitude distortion become significant.
The width of each angle bin, in degrees. The number of output traces equals (Max angle − Min angle) / Angle step. Default: 3°. Smaller steps produce more sub-stacks with higher angular resolution but lower fold; larger steps yield fewer, higher-fold stacks. Typical AVO values are 5–15°. Must not be zero.
Length of the running-average smoothing window applied to the angle gather in the time direction before bin assignment, in seconds. Default: 0.01 s (10 ms). Increase to 20–50 ms if the angle gather shows significant sample-to-sample variability. Setting to zero disables smoothing. This smoothing applies only to the angle field used for bin assignment; it does not alter the NMO amplitude data.