Expanding spread profiles across the Trans-Hudson Orogen

Sándor Bezdán, Zoltan Hajnal

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3 Citations (Scopus)


Four vibroseis expanding spread profiles (ESP) were acquired through the LITHOPROBE Trans-Hudson Orogen Transect program. These ESP's, with a maximum offset of 20 km, were centred on areas where prominent crustal reflectivity was detected by the regional survey. The small source stepout distance (100 m) generated high-fold (> 30) data. The Common Midpoint (CMP) stacked sections of ESP and regional reflection data of the 1991 survey exhibit similar crustal images. The regional profiles provide better resolution of shallow and dipping features, whereas the continuity and strength of rejections below 6 s two-way travellings (TWT) are better defined on the ESP sections. Modelling results reveal that velocity estimation becomes more robust and accurate when crustal seismic surveys utilize longer offsets than commonly implemented by standard practice. These larger source-receiver separations, however, must be generally limited to offset/depth ratios not exceeding 1.5 when conventional velocity analysis techniques, based on the hyperbolic moveout assumptions, are implemented. The advantages provided by the long-offset data acquisition include increased S/N ratio and a greater number of traces with sufficiently large moveouts which improve velocity resolution, especially below mid-crustal depths. To achieve similar advantages in a regional crustal reflection survey would require the adoption of longer spread lengths than those presently implemented in standard data acquisition procedures.

Original languageEnglish
Pages (from-to)83-91
Number of pages9
Issue number1-4
Publication statusPublished - Mar 30 1998



  • Canada
  • Crustal reflection technique
  • Large offsets

ASJC Scopus subject areas

  • Geophysics
  • Earth-Surface Processes

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