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<< Click to Display Table of Contents >> Navigation: Velocity > Align gather to horizon |
Flattens a seismic gather by shifting each trace in time so that a selected interpreted horizon appears as a horizontal flat event across the gather. This is useful for quality control of velocity picks, AVO (Amplitude Versus Offset) analysis, and any workflow where examining the relative amplitude or wavelet character along a specific reflector is required.
For each trace in the gather, the module reads the two-way travel time of the selected horizon at the trace bin location. It then computes a time shift equal to the difference between the maximum horizon time across all traces and the horizon time at that individual trace. Applying these shifts causes the horizon to align at a common flat level equal to the maximum horizon time observed in the gather. Trace shifting is performed using an 8-point sinc interpolation method to preserve wavelet shape and avoid aliasing artefacts.
The Reverse direction option undoes the alignment, restoring gather traces to their original time positions. This is typically applied downstream after an operation on the flattened gather — such as noise attenuation or amplitude extraction — to restore correct time geometry for subsequent processing steps.
Note: This module expects the input data to be on a common datum. If source and receiver datum elevations differ between traces, a warning will be issued and alignment results may be inconsistent.
The seismic gather to be aligned. Typically a CMP, CRP, or shot gather containing multiple offset traces. Each trace must carry bin coordinates (X, Y) so that the module can look up the horizon time at the correct map location. The gather should already be corrected to a common datum before applying this module.
The interpreted horizon dataset containing one or more picked horizon layers. The module queries this dataset at the bin (X, Y) position of each trace to obtain the two-way travel time of the selected horizon. The horizon must have valid picks covering the area of the input gather; traces at unpicked locations receive a zero shift. Typically produced by an interpretation or auto-picking module upstream in the workflow.
Controls whether the module flattens the gather or restores it to its original time positions.
Forward (default) — shifts each trace so that the selected horizon aligns to a flat, common time level across the gather.
Reverse — applies the same time shifts with opposite sign, returning traces to their pre-alignment positions. Use this after completing analysis on the flattened gather to restore the correct time geometry for subsequent workflow steps.
The zero-based index of the horizon layer to align to. If the input horizon dataset contains multiple interpreted layers, this parameter selects which one is used as the alignment reference. Default: 0 (first layer). Set to 1 for the second layer, 2 for the third, and so on. If the index is out of range, the module reports an error and stops processing.
The time-shifted gather with the selected horizon aligned to a flat level (Forward mode), or with the original time geometry restored (Reverse mode). The output has the same number of traces and samples as the input; trace headers and geometry information are preserved unchanged.