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DEPRECATED: This module is deprecated and should not be used in new processing workflows. It is retained only for compatibility with legacy projects.
The Translate some types of velocities (3D) module performs bulk conversion between different velocity representations for 3D seismic data. Starting from a 3D velocity volume stored in SEG-Y format, the module can convert between five velocity types: interval velocity in time (VINT Time), interval velocity in depth (VINT Depth), RMS velocity in time (VRMS), average velocity in time (VAVG Time), and back again. The output is written to a new SEG-Y file with user-specified sampling in either the time or depth domain.
The supported conversion directions are: VINT Time to Depth — converts time-domain interval velocity to depth-domain interval velocity; VINT Depth to Time — the inverse conversion; VINT Time to RMS — computes RMS velocity from interval velocity using the forward Dix integral; VINT Time to VAVG Time — computes average velocity in the time domain; and VAVG Time to VINT Time — recovers interval velocity from average velocity. A replacement velocity and datum are used to handle the near-surface layer above the first pick.
The trace header collection for the 3D velocity volume. Headers supply inline/crossline coordinates and datum elevation values used during the conversion.
A handle to the SEG-Y file containing the input 3D velocity volume. The module reads velocity traces directly from this file and converts them according to the selected processing method.
The path and filename for the output SEG-Y file that will receive the converted velocity volume. Must have a .sgy or .segy extension. Ensure that the target directory exists and has sufficient disk space for the output volume.
The number of samples in each output velocity trace. Default: 2000. For depth-domain output (VINT Time to Depth), this determines the total depth extent of the output in combination with the dz parameter. For time-domain output, it determines the total record length in combination with dt.
The time sample interval for time-domain output traces, in seconds. Default: 0.004 s (4 ms). This parameter controls the output sampling when the processing method produces a time-domain result (such as VINT Depth to Time or VINT Time to RMS). Set this to match the sample interval of the target seismic data.
The depth sample interval for depth-domain output traces, in metres. Default: 5 m. This parameter controls the output sampling when the processing method produces a depth-domain result (VINT Time to Depth). Set this to match the depth interval of the target depth-domain model or migrated volume.
Selects the velocity conversion to perform. Default: VINT Time 2 RMS. Available options:
VINT Time 2 Depth — converts interval velocity as a function of two-way time to interval velocity as a function of depth, using the datum and replacement velocity for the near-surface. Use this when preparing a depth velocity model for PSDM.
VINT Depth 2 Time — the inverse operation: converts depth-domain interval velocity back to time-domain interval velocity. Use this to convert a PSDM velocity model back to a time-domain representation.
VINT Time 2 RMS — computes RMS velocity from time-domain interval velocity using the Dix integral. The result can be used for NMO correction or as input to PSTM migration.
VINT Time 2 VAVG Time — computes average velocity as a function of two-way time from time-domain interval velocity. Average velocity equals total depth divided by one-way travel time at each sample.
VAVG Time 2 VINT Time — recovers time-domain interval velocity from average velocity by differentiation. Note that this inverse operation amplifies high-frequency noise in the input; ensure the input average velocity field is smooth before applying this method.
The reference datum elevation (in metres) used when converting between time and depth domains. The replacement velocity is applied from the surface down to this datum elevation. Default: -99999.9, which causes the module to automatically detect the datum as the maximum receiver datum elevation found in the input trace headers. Set this manually if you require a fixed flat datum.
The velocity value (in m/s) assumed for the near-surface layer between the ground surface and the datum. Default: 1500 m/s. This value is used to compute the travel time through the weathering layer when converting between time and depth. Use the local near-surface velocity or weathering velocity for the survey area. Typical values range from 300 m/s (soft sediments) to 2000 m/s (consolidated rock).