--> --> The Influence of the Relative Orientation of Multi-Phase Rifting on Fault Growth and Interaction
[First Hit]

AAPG Annual Convention and Exhibition

Datapages, Inc.Print this page

The Influence of the Relative Orientation of Multi-Previous HitPhaseNext Hit Rifting on Fault Growth and Interaction

Abstract

It is known that rifted basins experience multiple phases of extension during their evolution where both the orientation and rate of extension vary through time. This has been examined by the application of physical analogue modelling to the evolution of rifting in these environments. The full three-dimensional geometrical relationship between the growth and interaction of the evolving fault network, however, is difficult to fully investigate and constrain from this technique. A 3D numerical model has been developed that addresses the growth and interaction of normal faults in a multi-Previous HitphaseNext Hit environment. The crust is represented by spherical elements in a two-layer system with both brittle and ductile interactions between elements, where gravitational and isostatic forces are included. Faults are defined through the displacement between particle pairs and their growth, interaction and throw are recorded through time. As a consequence, specific interactions between pairs or groups of faults can be highlighted and investigated. The time at which bonds fail on faults is also recorded which permits investigation of the timing of fault activity relative to the two-Previous HitphaseNext Hit system. This study examines the relationship between the orientation of Previous HitPhaseNext Hit I and Previous HitPhaseNext Hit II extension on the resulting fault population. Previous HitPhaseNext Hit I faulting is carried out for 15% extension of the basin. Following this, a further 15% extension is carried out at varying orientations between 10 and 80 degrees to Previous HitPhaseNext Hit I. Faults that develop in Previous HitPhaseNext Hit I form through the lateral propagation and linkage of smaller faults and appear in conjugate sets perpendicular to the extension direction. At the initiation of Previous HitPhaseNext Hit II, the primary location of continued fault growth and propagation is focussed on the tips and relays between Previous HitPhaseNext Hit I faults. Continued Previous HitPhaseNext Hit II extension results in the rotation of the alignment of faulting into the Previous HitPhaseNext Hit II orientation where later Previous HitPhaseNext Hit II faults bisect and connect existing Previous HitPhaseNext Hit I structures. Some Previous HitPhaseNext Hit I faults are active or reactivated within Previous HitPhaseNext Hit II depending on the relative orientation of the two phases. The distribution of faulting exhibits a fabric with depth, where faulting lower in the brittle crust shows a strong link with the Previous HitPhaseNext Hit I orientation, where short Previous HitPhaseNext Hit II orientated failure is observed at the fault tips. Rising through the brittle layer results in an increase in the number of faults present in both Previous HitPhaseNext Hit I and Previous HitPhaseTop II orientations.