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Mistie correction#

Compensate mistie for SEG-Y file(s) via cross-correlation of nearest traces of intersecting lines.

Description#

This script corrects the vertical mistie at profile intersections by calculating an individual (i.e. global) bulk shift value for each input profile using least-squars minimization. In case of several overlapping profiles with many intersections, this closed-loop configuration (Harper, 1991) can be represented as a set of over-determined equations and solved following the approach proposed by Bishop and Nunns (1994).

Mistie (in time domain) for individual TOPAS profiles

Figure 1: Mistie (in time domain) for individual TOPAS profiles (left).

The general workflow is summarized in the following steps:

  1. Calclulate profile intersections
  2. Extract nearest trace(s) at intersections based on euclidean distance (optionally in user-defined vertical window)
  3. Create reference trace from nearest traces (reduce effect of noisy traces)
    • calculating trace envelope for more performant cross-correlation
  4. Compute cross-correlation of reference traces
  5. Remove low-quality cross-correlation using an user-defined quality threshold (Pearson's correlation coefficient in SciPy)
  6. Calculate single bulk shift value for each profile using least-squares minimization
  7. Apply bulk shift (for individual lines)

Mistie (in time domain) for individual TOPAS profiles Mistie (in time domain) for individual TOPAS profiles

Figure 2: Conceptual mistie correction at intersection of two examplary profiles.

Usage#

This script is designed to be used from the terminal (i.e. command line).

Command line interface#

The script can handle two different inputs:

  1. datalist of files to process (e.g., datalist.txt)
  2. directory with input files (e.g., /input_dir)

There are two options to run the script. We recommend using the CLI entry point like:

>>> 07_correct_mistie {filename.sgy | datalist.txt | </directory>} [optional parameters]

Alternatively, the script can be executed using the (more verbose) command:

>>> python -m pseudo_3D_interpolation.mistie_correction_segy {filename.sgy | datalist.txt | </directory>} [optional parameters]

Optionally, the following parameters can be specified:

  • --help, -h: Show help.
  • --output_dir {DIR}: Output directory (either --inplace or --output_dir are required!).
  • --inplace: Replace input data without creating copy (either --inplace or --output_dir are required!).
  • --suffix {sgy}: File suffix (default: sgy). Only used if directory is specified.
  • --filename_suffix {SUFFIX}: Filename suffix (e.g. pad, static) to filter input files. Only used if directory is specified.
  • --txt_suffix {despk}: Suffix to append to output filename (default: despk).
  • --coords_origin: Origin of (shotpoint) coordinates (i.e. navigation).
    • header (default): Extract coordinates from SEG-Y header(s).
    • aux: Read previously extracted coordinates from auxiliary file.
  • --coords_path: Path to SEG-Y directory (coords_origin=header) or navigation file with coordinates (coords_origin=aux)
  • --win_cc: Upper/lower trace window limits used for cross-correlation (in ms), e.g., for using only seafloor reflection.
  • --quality_threshold: Cut-off threshold for cross-correlation [0-1] used to remove noisy/insufficient intersections.
  • --write_aux: Write mistie offsets to auxiliary file (*.mst).
  • --write_QC: Write line intersections and nearest traces to GeoPackage (*.gpkg).
  • --verbose {LEVEL}, -V: Level of output verbosity (default: 0).

References#

  • Harper, Michael D. 1991. “Seismic Mis‐tie Resolution Technique.” Geophysics 56 (11): 1825–30. https://doi.org/10.1190/1.1442995.
  • Bishop, Thomas N., and Alan G. Nunns. 1994. “Correcting Amplitude, Time, and Phase Mis‐ties in Seismic Data.” Geophysics 59 (6): 946–53. https://doi.org/10.1190/1.1443654.
Last update: Monday, 03 July 2023 at 09:46:51