Kinematic 3D Retro-Deformation of Fault Blocks Picked from 3D Seismics

Abstract

Movement on fault planes causes a large amount of smaller-scale deformation, ductile or brittle, in the area surrounding the fault. Much of this deformation is below the resolution of reflection seismics (i.e. sub-seismic, <10m displacement), but it is important to determine this deformation, since it can make up a large portion of the total bulk strain, for instance in a developing sedimentary basin. Calculation of the amount of sub-seismic strain around a fault by 3-D geometrical kinematic retro-deformation can also be used to predict the orientation and magnitude of these smaller-scale structures. However, firstly a 3-D model of the fault and its faulted horizons must be constructed at a high enough resolution to be able to preserve fault and horizon morphology with a grid spacing of less than 10 m. Secondly, the kinematics of the fault need to be determined, and thirdly a suitable deformation algorithm chosen to fit the deformation style. Then by restoring the faulted horizons to their pre-deformation state (a ‘regional’), the moved horizons can be interrogated as to the strain they underwent. Since strain is commutative, the deformation demonstrated during this retro-deformation is equivalent to that during the natural, forward deformation...