Three-dimensional geometry and growth of conjugate normal faults

• Published in: Journal of structural geology Vol. 17; no. 6; pp. 847,851 - 849,862
• Main Authors: Nicol, A., Walsh, J.J., Watterson, J., Bretan, P.G.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01-06-1995
• ISSN: 0191-8141; 1873-1201
• DOI: 10.1016/0191-8141(94)00109-D

Good quality 2-D and 3-D seismic reflection data from the Timor Sea are used to determine the threedimensional geometry, displacement patterns and development of intersecting conjugate normal faults. These data are supplemented by data from previous physical modelling studies. Conjugate structures, which comprise two intersecting opposed-dipping normal faults or fault sets, form synchronously on a geological time scale and develop due to the incidental intersection of the faults, factors which affect both the formation and imaging of these structures include: the fault density, the spatial distribution of opposed-dipping faults, the seismic resolution and the vertical extent of the imaged fault data. Large conjugate structures grow from smaller ones; larger conjugates are associated with more numerous and larger faults than small structures. On the scale of the seismic data (fault throws range from ca 10–400 m). synchronous fault movements are accommodated by a reduction of displacements on discrete fault surfaces towards the fault intersection zone, and a corresponding increase in ductile strain of this region. High strains in the volume proximal to the fault intersection zone are expressed as thinning of stratigraphic units between the conjugate faults, and are believed to be accommodated by numerous small sub-seismic faults. Intersection of two opposed-dipping faults does not prevent their continued synchronous movement and does not result in mechanical locking of the system.