Evolution of a fault surface from 3D attribute analysis and displacement measurements

A large fault surface evolves by growth and coalescence of numerous segments through time, which results in strong undulations of the principal fault surface. We interpreted a strongly segmented, 13 km long fault using 3D seismic data, and studied the morphology in terms of fault linkage, using curvature, azimuth, and dip attributes. Displacement profiles of two horizons were measured to analyse the different displacement relations and to quantify their variation and dependence on fault morphology.We identified four orders of fault segments over a scale range from a few hundred metres to several kilometres, which evolved during fault growth. The strong changes in orientation of the several segments might result in a heterogeneous small-scale fracture distribution and different fault drag geometries. Displacement measurements on the undulated fault surface indicate a strong variation between real, vertical, and horizontal displacement values. However, the commonly used throw values lead to a smoothing of the real displacement curves and to an underrepresentation of their values, and therefore cannot show a triangular shape that is typically identified from ruptures fault surfaces of earthquake processes. Therefore, for any kind of fault analysis care should be taken when using throw as approximation for the real displacement.