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Identification of Strike-Slip Faults in Seismic Sections

Pedro Victor Zalan

Transcurrent tectonism has been extensively reviewed in the literature during the last three decades, and its structural style in horizontal sections is well known. The increasingly large amount of seismic data available in the sedimentary basins all over the world has shown that transcurrent faults have very well defined characteristics in vertical sections as well.

The main criteria used in identifying strike-slip faults in seismic sections are (1) flower structures (positive or negative), (2) change from normal to reverse fault along strike, (3) upthrown block switching side along strike, (4) change in the amount and/or direction of dip of fault plane along strike, (5) reversal of or change in fault throw with depth, (6) abrupt changes in the nature of seismic facies across the fault, (7) abrupt changes in the thickness of seismic facies or stratigraphic intervals across the fault, (8) abrupt changes in styles and/or intensities of deformation across the fault, and (9) complex geometries of the fault plane. Although one of these criteria (flower structures) can be reliably used as a definitive indicator, the others must be employed collectively to determine the transcurrent character of a fault zone.

The usefulness of these criteria lies in the fact that a small number of seismic sections (two or three, sometimes even a single one), largely spaced and crossing the fault zone at great angles, is enough to determine the existence of wrench tectonism in a target area. Such recognition has important economic implications because it increases the variety of potential traps that can possibly exist along the fault trend.

AAPG Search and Discovery Article #91038©1987 AAPG Annual Convention, Los Angeles, California, June 7-10, 1987.