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<< Click to Display Table of Contents >> Navigation: MultiFocusing > MFParams to times arrivals (common offset) |
Note: This module is deprecated. It is retained for compatibility with existing workflows.
This module converts multi-focusing (MF) parameter gathers stored as common-offset SEG-Y files on disk into tomographic time arrivals. Unlike the zero-offset variant, this module reads its input data directly from a directory of common-offset SEG-Y files: for each offset class it expects separate files containing the stack, source-angle, receiver-angle, and correlation gathers (identified by filename prefix conventions such as stack_, betasource_, betareceiver_, and correlation_). For each detected reflector in each offset class the module reconstructs source and receiver positions from the multi-focusing angles and writes the travel times as tomographic pick records to an output tomo item.
Use this module when multi-focusing results have been saved as common-offset gathers to disk rather than passed as live connections in the processing flow. The output tomo item feeds into a tomographic velocity inversion workflow to update the subsurface velocity model.
This module reads all input data from SEG-Y files on disk. There are no live gather connections. All input is configured through the Input directory parameter.
The path to any one of the common-offset SEG-Y files in the input directory. The module automatically discovers all SEG-Y files in the same directory and groups them by offset class based on a numeric suffix in their filename. Each offset group must contain files named with the prefixes stack_, betasource_, betareceiver_, and (optionally) correlation_. Browse to the directory and select any representative SEG-Y file to register the input location.
Selects the reflector detection algorithm. Fast (default) scans the semblance gather using a sliding window and picks the maximum semblance value within each window cell, producing a reduced but quickly computed set of picks. Long performs a more exhaustive search over all sample positions and de-duplicates results; this is more accurate but significantly slower on large datasets.
The half-width of the spatial search window (in traces) used when detecting local semblance maxima. The default is 10 traces. Increase this value for datasets with large midpoint spacing to ensure each reflector is captured at least once per window. Reduce it for densely sampled data to improve lateral resolution of the picks.
The half-width of the time search window (in samples) used when detecting local semblance maxima. The default is 10 samples. Increase this value to merge closely spaced reflection events into a single pick. Reduce it to resolve thin layers with tightly spaced events.
The near-surface velocity (m/s) used to compute travel times along reconstructed ray paths and to determine the minimum arrival time offset for each common-offset class. The default is 1500 m/s. Set this to the best available estimate of the near-surface velocity in the survey area.
The minimum semblance value (dimensionless, 0–1) a candidate reflector must exceed in the correlation gather to be included in the output. The default is 0.05. Increase this value to restrict picks to high-confidence reflectors. Decrease it if the tomographic inversion requires more picks to achieve adequate coverage.
The minimum absolute amplitude value a candidate reflector must exceed in the stack gather to be included in the output. The default is 0.005. This filter removes low-amplitude noise events that pass the semblance threshold but do not correspond to meaningful reflection arrivals.
The path and filename for the output tomographic picks file. Browse to the desired output directory and enter a filename. The file records source and receiver positions, emergence angles, and travel times for all detected reflectors across all processed common-offset classes.