| OpendTect User Documentation version 3.2 |
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Name
Delta Resample -- Attribute that enables residual alignment of seismic volumes
Description
This attribute is used to make shifts inside seismic volumes. By defining an input cube and a delta cube, which represents the shifts that should be applied to the input data, a correctly aligned output volume can be generated. The delta cube can be generated by using the attribute "Match Delta". Using the "Delta Resample" attribute is very useful in case of working on, for example, multi-azimuth volumes which frequently show some degree of misalignment. This technique can also be very useful for time-lapse seismic data and NMO-corrected data. Only after aligning, a correct comparison can be made between two different volumes.
The delta cube can be generated by using the Match Delta attribute. An advanced option in the attribute engine is that, when the input is periodic and contains phases, it is possible to define a (maximum) period. The box "Input is periodic" should be clicked and the period should be defined in the box. However, a situation like that is very exceptional and, in 99 out of 100 cases, the shift can be applied without using this option.
One of the side-effects of this residual alignment is that existing horizons are not consistent with the data any more. The horizons should be re-snapped to the aligned seismic data by using the option "Algorithms" when right-clicking a horizon in the tree. The third option "Snap to event" enables the user to make the horizon consistent again. Only after snapping the horizons can the user, for example, calculate horizon-steered attributes or performing waveform segmentation.