Interpretation validation on vertically exaggerated reflection seismic sections

Abstract

Reflection seismic data is usually displayed with a vertical exaggeration factor in the range 2–6 irrespective of whether it is time or depth domain data. This vertical exaggeration gives certain advantages to stratigraphic and structural interpretation, and is sometimes a prerequisite to view long-wavelength structures. However, vertical exaggeration distorts geological structures, affecting dip, curvature, line length, cross-sectional area, volume and angular relationships. Reflection seismic can be assigned a “vertical exaggeration heterogeneity factor” based on the extremes of seismic velocities. In the absence of appreciable poorly-compacted units and bathymetry, and generally on depth domain data, vertical exaggeration is relatively homogeneous. Analytical solutions are derived to quantify the distortion of angular relationships, curvature and bed thickness under homogeneous vertical exaggeration. Modelled extensional and compressional geometries give acceptable area balance restorations using vertical shear under homogeneous vertical exaggeration. These vertically exaggerated restorations are neither admissible nor viable because the deformed and restored state sections are unrealistic. Given low heterogeneity of vertical exaggeration, and relatively simple structure that typifies many extensional geometries and some thrust geometries, aspect ratios of 1:1 are not definitively required for section validation by restoration.