Abstract - Previous studies of listric growth fault evolution have, to a large extent, relied on scaled analogue models in which a deformable hangingwall is displaced over a fixed, rigid footwall block. Such boundary conditions are, however, unlikely to be satisfied in many natural fault systems. We describe the structural evolution of a listric growth fault system from SE Asia, using data from a high-resolution 3-D seismic survey. The fault system shows systematic changes in geometry that are sympathetic with along-strike changes in the nature of the basal detachment fault. Where the basal detachment fault remained fixed throughout extension, hangingwall rollover and associated growth faults show only limited migration towards the bounding detachment fault. Along strike, however, three phases of footwall collapse, with backstepping of the basal detachment into the footwall block, are responsible for migration of both the rollover axis and associated growth faults towards the footwall block during extension. Deformation above the backstepping detachment was characterised by punctuated, i.e. stepwise, migration of the rollover axis and growth faults towards the footwall, arising from each phase of footwall collapse. Since the migration of hangingwall structures is similar to that observed within analogue models with fixed detachment surfaces, care should be taken in defining kinematic models in areas where the geometry of the bounding fault is either poorly defined or unknown. This study demonstrates the importance of footwall collapse in the development of natural listric growth fault systems, and highlights the differences between systems with ‘fixed’ and ‘backstepping’ basal detachment faults.
Abstract of talk given to:
Tectonic Studies Group Annual Meeting, Tectonic Studies Group, University of Leeds, January 2001