Conventional fault seal methods derive transmissibility properties of faults by calculating the shale gouge ratio along the fault. Fault thickness is a key parameter. However, the method does not consider intrinsic fault complexities, such as lenses, varying fault rocks and diagenetic elements. In this study we present a characterization of fault cores in carbonates, based on an analysis of fault composition with respect to the displacement/thickness relationship (D/T). Using a Fault Facies type description of rocks we have compiled and analysed the dimensions and composition of 100 faults cores from Sinai, Oman and Svalbard. These areas display thick succession of sedimentary carbonates truncated by extensional faults. Common volumetric elements of the cores (core facies) include fault rocks such as breccias, calcareous gouge and shale gouge (smear) and layers of calcite precipitated on the walls of slip-surfaces. The overall increase in thickness relative to displacement, showing a lower increase of fault thickness for large scale faults than for small scale faults, fits a power law distribution with an exponent lower than one. The individual fault core facies display different D/T than the overall D/T relationship, indicating that protolith, diagenetic effects and tectonic environment influence the observed thickness increase.


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