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RTM imaging performs Reverse Time Migration on pre-stack seismic data to produce a depth-domain image. The module reads source and receiver SEG-Y data, forward-propagates the source wavefield and back-propagates the receiver wavefield through a depth interval velocity model, and applies a zero-lag cross-correlation imaging condition to produce the migrated image. It supports both source-ordered and receiver-ordered input data, optional mute picking on source and receiver gathers before migration, and a sub-sequence of pre-processing steps applied to each gather before migration. The output includes the depth-domain stacked image and optional time-domain images, along with intermediate source and receiver wavefields for QC.
The SEG-Y file handle for the primary (source-side) input dataset. Connect this to the output SEG-Y handle from the reading module in the workflow.
The trace header vector for the primary input dataset, providing geometry and sorting information for each trace. Connect this to the corresponding trace headers output from the reading module.
An optional secondary SEG-Y file handle used for illumination compensation. When connected, the module uses this dataset to compute an illumination correction that normalises the migrated image for uneven source-receiver coverage.
The trace header vector for the illumination input dataset. Connect alongside Input SEG-Y data handle illum when illumination compensation is used.
The depth-domain interval velocity model used to propagate wavefields during migration. Connect this to the output of a velocity model builder, tomography, or FWI module. The velocity field must cover the full depth range of the migration aperture.
Optional mute curve for the source gathers. When connected, this mute is applied to each source gather before wavefield propagation, suppressing direct wave energy or other noise above the defined mute boundary.
Optional mute curve for the receiver gathers. Applied analogously to the source mute, suppressing noise on the receiver side before back-propagation.
Specifies how source gathers are assembled from the input SEG-Y. The default is Abs offset. Select Offset or Abs offset to sort traces by their signed or absolute offset within each source gather; select RCV to sort by receiver position for receiver-domain processing.
Specifies how receiver gathers are assembled from the input SEG-Y. The default is Abs offset. Analogous to SRC sort by but controls the receiver-side gather assembly.
When enabled (default: false), the migration image is accumulated on a receiver-by-receiver basis rather than source-by-source. Enable this option when the input data is sorted by receiver and the receiver wavefield is the primary forward-propagated field.
Container group for mute picking parameters. Mute curves can be picked interactively on the source and receiver gather displays within this module and applied to suppress noise before propagation.
The spatial taper width (in metres) applied at the edges of the model to suppress boundary reflections during wavefield extrapolation. The default is 20 m. Increasing this value provides a more gradual absorbing boundary and reduces edge artefacts in the migrated image at the cost of a wider padding zone.
Container group for parameters controlling the import of external mute picks from a file. Use this to load pre-existing mute curves computed outside the module.
When enabled (default: true), interactively picked mute points are snapped to the nearest trace position in the gather geometry. This prevents mute picks from being placed between actual trace positions, ensuring that the mute boundary aligns with the data.
The maximum snapping distance (in metres) for the Magnet picking points to geometry option. The default is 50 m. Picked points further than this distance from any trace position will not be snapped.
The time sample interval (in seconds) of the time-domain output gathers. The default is 0.004 s (4 ms). This controls the sampling rate of the optional time-domain output images; it does not affect the depth-domain image which is controlled by the velocity model grid spacing.
The total record length (in seconds) of the time-domain output gathers. The default is 5 s. Set this to match the maximum two-way travel time of the deepest target plus a margin for the mute zone.
The near-surface replacement velocity (in m/s) used to convert between the depth datum and the time output. The default is 2000 m/s. This value fills the zone between the surface and the datum, analogous to the replacement velocity in static corrections.
The output datum elevation (in metres) for the depth-domain migrated image. The default is 0 m (sea level). Set this to the survey datum elevation to align the depth output with the coordinate reference frame of the project.
When enabled (default: true), applies a post-migration mute to suppress migration operator smear and direct-wave artefacts in the shallow part of the image. Disable this only for diagnostic purposes when inspecting the full un-muted output.
When enabled (default: true), the output image is cropped to the actual topographic surface at each position, removing samples above the free surface. This prevents erroneous image energy appearing above ground level for surveys with significant topographic relief.
When enabled (default: false), the module outputs a difference gather showing the change between the input and output, useful for QC of the imaging operator. Disable this in production to save memory and I/O.
When enabled (default: true), applies a f-f (frequency-frequency) filter to the migrated image as a post-processing step to suppress low-frequency migration noise and improve image quality. The strength of this filter is controlled by FF power.
The exponent applied in the f-f filter when Use ff filter is enabled. The default is 1. Higher values apply a stronger high-pass effect to the image, further suppressing low-frequency migration artefacts but potentially affecting shallow low-frequency signal.
A constant phase rotation (in degrees) applied to the migrated image after all other post-processing steps. The default is 0 (no rotation). Use this to correct for a known phase error in the source wavelet or to convert between minimum-phase and zero-phase images. Set to 90 degrees for a Hilbert transform effect.
When enabled (default: true), applies amplitude normalisation to the migrated image to compensate for depth-dependent energy decay and uneven illumination. Disable this only if you need to preserve the true amplitude scaling of the imaging condition for AVO or amplitude extraction purposes.
Container for SEG-Y reading parameters controlling byte-swap, trace header byte locations, and other format options for reading the input SEG-Y files. Adjust these if the input data does not conform to standard SEG-Y Rev 1 header layout.
Selects whether the RTM wavefield propagation is executed on the CPU or GPU. GPU execution significantly accelerates the migration, particularly for 3D or large 2D datasets. Requires a compatible CUDA-capable GPU with sufficient VRAM to hold the velocity model and wavefield snapshots.
Options for distributing the migration across multiple compute nodes. Enable this to specify a cluster configuration for large-scale RTM runs where a single node does not have sufficient memory or compute capacity.
The number of shot gathers processed per distributed computing chunk. Larger values reduce inter-node communication overhead but require more memory per node. Adjust based on the available memory on each compute node.
The maximum number of CPU threads used per compute node in distributed mode. Setting this below the total number of available cores can reduce memory pressure when each thread requires a large memory allocation for wavefield storage.
A text suffix appended to the distributed job name to distinguish between concurrent migration runs on the same cluster. Use a unique suffix for each active workflow to avoid job name collisions.
When enabled, allows the user to specify a custom CPU affinity mask for the migration threads. Use this on NUMA systems to pin threads to specific processor sockets or cores to avoid cross-socket memory access penalties.
The CPU affinity mask or core specification string applied when Set custom affinity is enabled. Consult your system administrator for the correct format on your hardware configuration.
The number of CPU threads used for the migration when executing on CPU. Higher values use more cores for parallel wavefield propagation, reducing wall-clock time proportionally (up to available hardware threads). The default uses all available logical cores.
When enabled, bypasses this module entirely, passing the input data through to the output unchanged. Use this to temporarily disable the migration step during workflow testing without restructuring the processing graph.
The forward-propagated source wavefield snapshot at the current migration position, in the depth domain. Connect this to a display module for QC of the source wavefield propagation.
The back-propagated receiver wavefield snapshot at the current migration position, in the depth domain. Use for QC of the receiver wavefield propagation.
The forward-propagated source wavefield snapshot in the time domain, produced by depth-to-time conversion of the current source wavefield.
The back-propagated receiver wavefield snapshot in the time domain.
The illumination source wavefield in the depth domain, computed from the optional illumination input dataset. Used for illumination compensation of the migrated image.
The illumination receiver wavefield in the depth domain.
The illumination source wavefield in the time domain.
The illumination receiver wavefield in the time domain.
The per-shot contribution to the depth-domain migrated image from the current source gather (source-side imaging condition result).
The per-shot contribution to the depth-domain migrated image from the current receiver gather.
The per-shot source-side image contribution converted to the time domain.
The per-shot receiver-side image contribution converted to the time domain.
The final stacked RTM image in the depth domain, produced by summing all per-shot image contributions. This is the primary output of the module and the main deliverable for interpretation and velocity model QC.
The final stacked RTM image converted to the time domain using the depth velocity model. Useful for comparison with time-migrated results and for integrating with time-domain interpretation workflows.
Removes all interactively picked mute points from the source gather display, resetting the source mute to its default state.
Saves the current source mute picks to a file for use in subsequent processing runs or to share between workflows.
Loads source mute picks from a previously saved file.
Removes all interactively picked mute points from the receiver gather display.
Saves the current receiver mute picks to a file.
Loads receiver mute picks from a previously saved file.