|
<< Click to Display Table of Contents >> Navigation: Velocity > GUpdateV0FromDepthModelProcedure |
Note: This module is deprecated and is retained only for backward compatibility with older processing flows. It is not recommended for use in new projects.
This module updates the near-surface velocity (V0) stored in trace geometry headers — for every source point, receiver point, and bin point in the dataset — using a depth-domain velocity model gather as the reference. For each geometry point, the module finds the nearest velocity trace in the depth gather, then averages the velocity values over a shallow window just below the surface to derive a representative near-surface velocity. This averaged velocity is then written back into the geometry record for that point.
The module was used in refraction statics workflows where a near-surface velocity V0 needed to be derived directly from a depth velocity field rather than from first-break picking. The V0 value is extracted at the shallowest depth level in the velocity model where the velocity exceeds 3000 m/s, and the averaging window controls how many depth samples are used in the computation.
The geometry header table for the seismic dataset, containing source, receiver, and bin point coordinates and attributes. This is the primary input whose geometry records will be updated with near-surface velocity values. All source, receiver, and bin points present in this table will be processed.
An optional additional set of bin point locations to process alongside those contained in the trace headers. If connected, the near-surface velocity update is also applied to every bin point in this list, and the updated points are passed to the corresponding output. If not connected, this input is ignored.
The depth-domain velocity gather that serves as the reference velocity model. Each trace in this gather represents a vertical velocity profile at a specific surface location. For each geometry point being processed, the module selects the trace from this gather whose surface location is nearest to the point's coordinates, then extracts the near-surface velocity from that trace.
The number of depth samples used to compute the average near-surface velocity. The averaging window starts at the shallowest depth level in the velocity model where the velocity first exceeds 3000 m/s, and extends downward by this many samples. The averaged velocity over this window is then assigned as V0 to the geometry point. The default value is 10 samples. Increasing this value smooths out short-scale velocity variations in the shallow model; decreasing it makes V0 more sensitive to the exact depth of the first high-velocity layer. The window is automatically clipped if it extends beyond the available depth range of the velocity gather.
A copy of the input trace header table with the near-surface velocity attribute (V0) updated for all source, receiver, and bin points. All other header fields and geometry attributes remain unchanged.
The updated bin point list corresponding to the optional BinPointVector input. If the optional input was connected, this output contains the same bin points with their V0 values updated from the depth velocity model. If the optional input was not connected, this output is empty.