Local Trace Alignment
This process aligns gathers/records by applying a vertical shift to each trace. The shift is calculated using correlation to a target trace over a single window. When creating the target trace by stacking, the target is updated at each iteration using progressively higher frequencies.
- In the Process tab, click the blue "+" icon and select New Process.
- Select Local Trace Alignment and type a name for the process.
- Volume: Select the gather volume.
(Optional) Output header: If provided, store the final shift in this trace header.
- TIP: Use a scaled header (i.e. by SCALEL), to provide sub-ms precision. Stored shifts can be reversed using a "Trace Shift" process. When using an unscaled header, shifts are rounded to the nearest millisecond.
- Window top/bottom (ms): The start and end of the correlation window
Max shift per iteration (ms): The maximum time shift that can be applied.
- Choose a large enough value to flatten at the event.
- If values are too large, it may cycle-skip and correlate to the wrong event.
- Iterations: The number of iterations to perform. Each iteration filters the data using progressively-higher frequencies.
- High-cut on first/last frequencies: The first and last high-cut frequency values to apply. Iterations step linearly between these values.
- Central Traces: Align to the centre trace of the gather/record
- Stack of Traces: Align to a stack of the gather/record
(For Stack of Traces) Number of Stack Building Iterations:
- For the first iteration, the target is a stack of the input.
- For following iterations, the target is a stack of the input with shifts applied.
- Shifts are always calculated by correlating the original traces against the current target.