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Depth conversion transforms a post-stack seismic gather from the time domain into the depth domain using an RMS velocity model. Each trace is converted independently by sampling the velocity model at the trace's surface location (X, Y) to obtain the RMS velocity as a function of two-way travel time, and then mapping each time sample to a corresponding depth using the standard relation depth = V_rms * t / 2. Amplitude values are distributed into the depth grid by linear interpolation, preserving the seismic waveshape as accurately as possible during the stretch.
Use this module when you need to display or interpret stacked seismic data in depth rather than time, for example to tie seismic reflectors to well depth markers or to prepare data for depth-domain attribute extraction. The input gather must be post-stack (one trace per bin). Processing is performed in parallel across all traces for efficiency.
The post-stack seismic gather to convert. This must be a stacked (single-trace-per-bin) gather in the time domain. Pre-stack gathers (containing multiple offsets per bin) are not supported and will cause an error. Connect the output of a stack or any post-stack processing module here.
The RMS velocity model used to drive the time-to-depth conversion. The model is sampled at each trace location (X, Y) to produce a velocity-versus-time function for that trace. The accuracy of the depth conversion depends directly on the quality and spatial coverage of this velocity model. Connect a velocity model item built from a velocity analysis or velocity import module. The model must cover the full time range and spatial extent of the input seismic data.
The number of depth samples in the output gather. Default: 2000. The total depth range of the output is equal to the number of output samples multiplied by the depth step (Step Z). For example, with 2000 samples and a 5 m step, the output covers 0 to 10 000 m depth. Increase this value if the target reflectors are deeper than the current output range; decrease it to reduce file size when only shallow targets are of interest.
The depth spacing between consecutive output samples, in meters. Default: 5 m. Smaller values produce finer depth resolution and better preserve thin-bed character in the converted section, but result in larger output files. Larger values reduce file size but may cause aliasing of high-frequency content at shallow depths where the velocity is low and the time-to-depth mapping compresses rapidly. As a practical guide, choose a depth step that is no larger than half the minimum vertical wavelength expected in the data (V_min / (2 * f_max)).
The depth-domain seismic gather produced by the conversion. It has the same number of traces as the input gather, but the vertical axis is now depth (meters) with the sample interval set equal to the Step Z parameter. This gather is displayed in the Depth domain data view window. Connect it to downstream depth-domain processing or interpretation modules.
A quality-control gather showing the RMS velocity values that were actually used during the conversion, sampled from the velocity model at each trace location. This gather is in the time domain and is displayed together with the input seismic data in the Time domain data view window. Inspect this output to verify that the velocity model has been sampled correctly across the survey area and that no spatial gaps or anomalous values are present before trusting the converted depth section.