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<< Click to Display Table of Contents >> Navigation: Velocity > Detect VRMS mis-tie |
The Detect VRMS mis-tie module identifies seismic lines or gathers whose RMS velocity functions disagree significantly with a spatially interpolated velocity map constructed from all available input lines. This is a quality-control tool designed for multi-line or 3D-from-2D velocity reconciliation workflows, where velocity picks from independent 2D lines must be consistent at their geographic intersections and globally coherent across the survey area.
During execution, the module samples every input VRMS gather at a common time level (either a fixed time or a horizon surface), interpolates those velocity samples into a smooth 2D map, and then computes for each line the average fractional difference between the line's own VRMS values and the map. Lines whose average mis-tie exceeds the user-defined threshold are automatically flagged and routed to the Selected gathers output; all others appear in the Unselected gathers output. The analyst can review the per-line mis-tie map interactively, manually override the automatic classification by right-clicking on individual lines in the map view, and optionally use horizon-guided velocity filling to build a spatially consistent VRMS cube for downstream processing.
A typical use case is reconciling velocity picks from crossing 2D land or marine lines before merging them into a 3D velocity model. The module provides three interactive views: a location map showing line positions, color-coded intersection mis-ties, and per-line average mis-tie values; a velocity gather view for the currently selected line; and a table listing all flagged lines.
A collection of named VRMS velocity gathers, one per seismic line or survey segment. Each entry in the collection consists of a user-assigned Name label and a connected velocity gather item (post-stack format). The name is used to identify the line in the interactive map view and in the output table. Connect at least two lines to enable meaningful mis-tie analysis — the module finds geographic intersections between all pairs of connected lines and compares VRMS values at those crossing points. Each gather must carry valid trace coordinates (X, Y) in its trace headers so that the module can locate lines on the map and identify their intersections.
The fractional velocity mis-tie level above which a line is automatically classified as problematic. Default: 0.05 (5%). Range: 0 to 1 (0% to 100%). The mis-tie for each line is computed as the mean of |V_line - V_map| / max(V_line, V_map) over all traces where both the line velocity and the interpolated map velocity are valid. A value of 0.05 means any line whose average velocity deviates by more than 5% from the regional map is flagged. Lower the threshold to flag subtler anomalies; raise it to flag only severe outliers. Manual overrides applied interactively in the map view always take precedence over this automatic criterion.
This group controls what time level is used when sampling velocity values from each gather to build the reference velocity map and compute mis-tie scores. Because RMS velocity is a function of time, the comparison must be made at a consistent time across all lines. You can either use a single constant time for the entire survey or follow a picked horizon surface that adapts to the geology.
Selects how the reference time level is determined at each map location. Default: Fixed.
Fixed — the same two-way time value is used at every location across the survey. This is the simplest option and is appropriate when the geology is roughly flat-lying or when you want to compare velocities at a specific reservoir interval time. When this option is active, the Time parameter is shown.
Horizon — the comparison time follows a picked reflection horizon, so that velocity is always sampled just at a geologically meaningful interface regardless of structural relief. This mode is more accurate in areas with significant dip or structural complexity. When this option is active, the Horizon item and Horizon id parameters are shown and the Time parameter is hidden.
The two-way travel time (in seconds) at which all VRMS gathers are sampled when Time slice type is set to Fixed. Default: 0.5 s. Range: 0 to 100 s. Set this to a time that lies within the reservoir zone or at the key horizon of interest. Velocities are linearly interpolated between adjacent samples in the gather to obtain the value at the specified time.
A horizon picking item containing one or more interpreted time horizons, visible only when Time slice type is Horizon. The horizon must be in the time domain. After connecting a horizon item, the module builds an internal topography-corrected map of horizon times across the survey and uses those times as the per-location reference when sampling velocities. The horizon map is recomputed automatically whenever the connected item changes. If a horizon item is already loaded and you connect a new one, the module will ask whether to reinitialize.
The 1-based index of the horizon layer to use as the time slice reference when Time slice type is Horizon. Default: 1. If the connected horizon item contains multiple layers (e.g., Top Reservoir = 1, Base Reservoir = 2), select the layer whose time surface you wish to use as the comparison level. The module automatically clamps this value to the number of available layers.
This group controls the time axis and velocity range of the output VRMS cube that is created by the Create velocity by horizons custom action. These parameters define the regular grid in time on which the layered VRMS model is sampled and output as a gather. They have no effect on the mis-tie scoring or the automatic line selection.
The starting VRMS velocity (m/s) applied at time zero in the output cube. Default: 1500 m/s. This is also used when computing the topographic time shift applied to the horizon surfaces (shift = 2 * elevation / V0). Set this to a physically reasonable near-surface velocity for your survey area — typically the water velocity for marine data or the weathered-layer replacement velocity for land data.
The VRMS velocity (m/s) extrapolated to the end of the output cube time axis (Maximum time). Default: 6500 m/s. The velocity cube is filled by linear interpolation between the horizon-constrained velocity nodes; VEnd serves as the boundary condition beyond the last horizon. Set it to the expected deep velocity at the base of the model. Range: 1 to 440000 m/s.
The output sample interval (in seconds) for the VRMS velocity cube. Default: 0.1 s. The number of output samples is determined by Maximum time / DT. A coarser DT (e.g., 0.1 s) is sufficient for most velocity modeling purposes and keeps file sizes manageable. Use a finer value only if the output cube must match the sample rate of your seismic data exactly.
The total length (in seconds) of the output VRMS cube time axis. Default: 5 s. Set this to be at least as long as the deepest reflector of interest in your data. The cube is filled with linearly interpolated velocities from V0 at time zero through the horizon velocity nodes to VEnd at this maximum time.
Controls which group of lines is used as input when running the Fill velocity horizon by selected gathers custom action. Default: Selected.
Set to Selected if you want to build the horizon velocity model from the flagged (problematic or manually selected) lines — useful for investigating what those lines contribute. Set to Unselected to build the model from the trusted, well-behaved lines — the more common workflow when you want to produce a clean merged velocity model excluding outlier lines.
This group controls how the scatter of velocity samples from all input lines is interpolated into the 2D reference velocity map. The map is the baseline against which each individual line is compared. Better interpolation leads to a more accurate and representative reference map and therefore more meaningful mis-tie scores.
The grid cell size of the interpolated velocity map in the X (easting) direction, in meters. Default: 200 m. Range: 1 to 10000 m. A finer step produces a higher-resolution map but increases computation time. Set this to roughly the average line spacing or the spatial scale of velocity variations you wish to resolve. The same step is also used when constructing the topographic correction map and the per-horizon velocity surfaces.
The grid cell size of the interpolated velocity map in the Y (northing) direction, in meters. Default: 200 m. Range: 1 to 10000 m. Use the same value as Map step X for isotropic maps. For surveys with significantly different line spacings in the two directions, you may use different X and Y step values to match the data density.
A post-interpolation spatial smoothing radius applied to the velocity map in the X direction, in meters. Default: 0 m (no smoothing). Range: 0 to 100000 m. Increasing this value damps short-wavelength velocity anomalies in the reference map, making the mis-tie detection more sensitive to broad-scale velocity inconsistencies rather than local noise. Use smoothing when the input lines are noisy or sparse so that the reference map is geologically reasonable.
Post-interpolation spatial smoothing radius in the Y direction, in meters. Default: 0 m (no smoothing). Range: 0 to 100000 m. Smoothing is applied independently in X and Y, so you can use asymmetric windows to account for anisotropic line coverage.
The spatial interpolation algorithm used to build the reference velocity map from the scattered input velocity samples. Default: ABOS.
ABOS (Adaptive Bin-Based On-Smoothing) is a fast, distance-weighted gridding method well suited to irregularly spaced line data. It requires no additional parameters and works well when lines are distributed across the entire survey area.
Kriging is a geostatistical interpolation method that models spatial correlation through a variogram (covariance) model. It typically produces smoother, statistically optimal maps and is preferred when the velocity field is expected to be spatially correlated over long distances. When Kriging is selected, the Kriging covariance type, Kriging range, and Kriging number of points parameters become visible.
The variogram model shape used by the Kriging interpolator. Visible only when Interpolation type is Kriging. Default: Exponential. The Exponential model reaches its sill asymptotically and is suitable for gradual, continuously varying velocity fields. The Spherical model reaches its sill at the range distance and is preferred for phenomena with a clear decorrelation length. The Gaussian model has a parabolic behavior near the origin and is best when the velocity field is very smooth. For most velocity interpolation tasks, Exponential or Spherical are good defaults.
The spatial correlation range (in meters) for the Kriging variogram model. Visible only when Interpolation type is Kriging. Default: 100000 m. This is the distance beyond which velocity values are considered spatially uncorrelated. A large range (e.g., 100 km) produces a smoothly varying map with long-wavelength trends. Reduce the range to allow the map to follow shorter-wavelength velocity variations. Set it to approximately the characteristic lateral scale of velocity heterogeneity in your survey.
The number of nearest input data points used to estimate each output grid node during Kriging interpolation. Visible only when Interpolation type is Kriging. Default: 15. Minimum: 1. Using more points increases computation time but can improve map quality when data are dense. A value of 15 is a reliable general-purpose setting. Reduce it only if computation is too slow on very large datasets.
Selects the processing hardware. Default: CPU. The mis-tie detection and map interpolation are CPU-based operations; GPU mode is available for compatible downstream steps in a processing chain.
When enabled, the computation is distributed across multiple processing nodes in a cluster environment. Use this option for very large multi-line datasets where single-node computation would be too slow.
The minimum number of input lines processed per distributed job chunk. Relevant only when distributed execution is enabled. Larger values reduce scheduling overhead but may result in uneven load distribution.
When enabled in distributed mode, restricts the number of threads used on each cluster node to the value specified in the thread count field. Use this to prevent the job from monopolizing a shared compute node.
An optional text label appended to the distributed job name, used to distinguish multiple simultaneous jobs of the same type running on the cluster.
When enabled, restricts execution to a specific set of CPU cores defined by the Affinity mask. Use this on shared machines to isolate the job to dedicated cores and prevent interference with other running processes.
The CPU core affinity mask specifying which processor cores the module is allowed to use. Active only when Set custom affinity is enabled.
The number of parallel CPU threads used for multi-threaded operations such as Kriging interpolation and horizon surface construction. Increase this on multi-core machines to speed up processing. The module uses the thread count automatically when building the topographic map, interpolating horizon layers, and smoothing the velocity map.
When enabled, this module is bypassed entirely during processing flow execution. All input data is passed through unchanged and no mis-tie analysis is performed. Use this to temporarily disable the module without removing it from the processing chain.
A collection of named velocity gathers corresponding to the lines that were flagged as having a significant VRMS mis-tie — either automatically (mis-tie score exceeded the threshold) or manually (right-clicked in the map view). Each entry carries the line name and its VRMS gather. Connect this output to downstream modules that require the problematic lines for further investigation or reprocessing. The collection is fully rebuilt each time the module executes.
A collection of named velocity gathers for all lines that passed the mis-tie quality check — those whose average mis-tie score was below the threshold and that were not manually flagged. These represent the trusted, internally consistent lines. Connect this output to a merge or velocity model building module to produce a clean combined velocity field.
A tabular output listing the names of all lines classified as selected (flagged). This is a single-column table with a "Name" column. It is also shown interactively in the All selected lines table view panel. Use this table for reporting, documentation, or as a filter list in subsequent processing steps.
A spatially regularized VRMS velocity gather covering the full survey area, produced by the Create velocity by horizons custom action. Each trace in the output corresponds to one node of the interpolated velocity map grid, and its time axis runs from 0 to Maximum time at the DT sample interval. Velocity values are linearly interpolated in time between the horizon-constrained velocity nodes (built using Fill velocity horizon by selected gathers), anchored at V0 at time zero and VEnd at Maximum time. This output cube can be used directly as input to depth conversion, migration, or velocity model building modules.
The module provides three interactive view panels. The Location map panel shows all input line traces as points on an XY plan view, color-coded by their per-line average mis-tie percentage (Line average misfits), with line velocity values and intersection mis-tie magnitudes also available as overlays. Left-click on a line to select it for detailed inspection. Right-click on a line to manually toggle its selected/unselected status. The currently selected line is highlighted by a distinct point style. The interpolated reference velocity map and, in Horizon mode, the current horizon time map can be displayed as colored matrix backgrounds. Intersection points between crossing lines are shown as colored dots whose value represents the absolute velocity difference between the two lines at that crossing.
The Selected line gather panel displays the VRMS velocity gather for the currently selected line, with the active time slice level overlaid as a curve (Time slice overlay) and any loaded horizon layers shown as additional horizon curves. This allows visual inspection of the velocity function quality and the time level at which the comparison is being made. In Horizon mode, use Shift+left-drag to un-exclude traces from a horizon velocity layer, and right-drag to mark traces as excluded from the per-horizon velocity build.
The All selected lines table panel lists the names of all currently flagged lines and updates in real time as you interactively select or deselect lines on the map.
Recomputes the reference velocity map from all connected input gathers using the current time slice level and interpolation settings, then refreshes the velocity map and mis-tie overlays in the location map view. Run this action after changing the Time, Interpolation type, or any interpolation parameter to see updated mis-tie scores without running a full execution.
Moves all currently selected (flagged) lines back to the unselected group and clears all manually applied horizon velocity data. A confirmation dialog is shown before clearing. Use this to reset the selection state and start the review process from scratch without re-executing the full module.
Saves the current horizon velocity picking data (per-horizon, per-line velocity assignments and excluded-trace masks) to a .dat file. Use this to archive the velocity editing session so it can be reloaded later without repeating the interactive picking work.
Loads previously saved horizon velocity picking data from a .dat file. The loaded data restores the per-horizon velocity assignments and excluded-trace masks that were saved by Save picking, allowing you to continue an editing session across multiple work sessions.
Samples the VRMS velocity from the currently active gather group (controlled by Selected/unselected gathers for creation) at the time corresponding to the currently active horizon layer, and stores those velocity values as the horizon velocity layer. Excluded-trace masks are respected, so only the non-excluded traces contribute to the layer. After this action, the horizon velocity layer is populated and the Horizons velocities map view is updated. Repeat this action for each horizon layer before running Create velocity by horizons.
Builds the output VRMS cube by assembling all filled horizon velocity layers into a time-continuous model. For each trace in the output map grid, the module collects the (time, velocity) pairs from all horizon layers that have been filled by Fill velocity horizon by selected gathers, adds the V0 boundary at time zero and VEnd at Maximum time, and fills the output trace by linear interpolation between these nodes. The resulting gather is stored in the Output VRMS cube output item. Run this action after all horizon layers have been filled. Requires that at least one horizon layer has both time and velocity data populated.