How do normal faults grow?

Abstract

Normal faults grow via synchronous increase in displacement and length ('propagating fault model', also known as the 'isolated fault model'), or by rapid length establishment and subsequent displacement accrual (constant-length fault model). We here use time-series displacement (D) and length (L) data from natural and experimental faults to elucidate growth styles and D-L trajectories throughout fault life, and to assess the applicability of the two fault models. We show that the growth of most faults is characterized by two stages, with the first defined by fault lengthening (20-30% of fault lifespan) and the second by displacement accrual (70-80% of fault lifespan). Although broadly adhering to the constant-length model, fault growth throughout the lengthening stage, during which significant displacement (10-60% of the total end-of-life fault displacement) may also accumulate, is achieved through rapid tip propagation, relay breaching, and segment linkage, characteristics perhaps most intuitively thought to reflect growth in accordance with the propagating model. The subsequent growth stage is dominated by displacement accrual with limited lateral tip propagation, a phenomenon best described by the constant-length model. We also show that, despite being used primarily in support of the propagating Rotevatn et al.-How do normal faults grow?

Extensional fault and fold growth: Impact on accommodation evolution and sedimentary infill

“…Considering the results of Manzocchi, Walsh, and Nicol (), the peak‐like displacement profile for base SU4 is likely generated by repeated rejuvenation of a single fault with a constant length or limited lengthening (Figure g). This agrees with Rotevatn, Jackson et al () in that faults will, to a varying degree, experience both lateral growth and throw focusing, albeit often in separate stages of their evolution. T‐X plots display short‐wavelength (1–2 km) variations superimposed onto basin‐scale (10–40 km) bell‐shapes (Figures e–g and a).…”

“…Thirty seismic horizons representing time‐markers were interpreted using DUG Insight 4, generally with an inline and crossline density of 5 but denser near the fault that was the focus of this study. The resulting geomodel, with a minimum grid resolution of 93.75 m × 62.5 m, has provided the basis for depth structure maps (Figure ), isochore thickness maps (Figure ), high‐resolution throw‐depth (T‐Z), expansion index (EI; Figure ) and throw‐length (T‐X) plots (Figure ), applying the methods outlined in Tvedt, Rotevatn, Jackson, Fossen, and Gawthorpe () and accounting for near‐fault deformation by projecting the interpreted horizons onto the fault based on the regional dip (see also Baudon & Cartwright, ; Childs, Nicol, Walsh, & Watterson, ; Dawers & Anders, ; Gawthorpe & Leeder, ; Jackson & Rotevatn, ; Mansfield & Cartwright, ; Rotevatn, Jackson, Tvedt, Bell, & Blækkan, ; Thorsen, ; Walsh & Watterson, ). We note uncertainties related to these methods such as burial compaction, thickness differences driven by nontectonic processes, erosion of footwall highs and underfilled basins as outlined in Jackson, Bell, Rotevatn, and Tvedt ().…”

Terrane Boundary Reactivation, Barriers to Lateral Fault Propagation and Reactivated Fabrics: Rifting Across the Median Batholith Zone, Great South Basin, New Zealand

“…Cumulative fault throw remains relatively constant across the system as it approaches the block, with a large displacement gradient present toward the boundary with the block itself (Figure 9). The relatively constant cumulative throw along the fault indicates a large degree of kinematic coherence within the system, with individual fault segments behaving as a singular system (Walsh & Watterson, 1991;Walsh et al, 2002;Walsh et al, 2003;Childs et al, 2017;Jackson et al, 2017;Rotevatn, Jackson, et al, 2018). In cross-section, some faults also appear linked at depth, forming a single structure indicative of some degree of geometric coherence (Figure 8) (Giba et al, 2012;Jackson et al, 2017;Walsh et al, 2003;Walsh & Watterson, 1991).…”

How do pre‐existing normal faults influence rift geometry? A comparison of adjacent basins with contrasting underlying structure on the Lofoten Margin, Norway

“…Childs, Watterson, & Walsh, ; Finch & Gawthorpe, ; Peacock & Sanderson, ; Walsh et al, ). Continued extension may result in fault linkage as a result of displacement accrual and relay rotation/breaching (Jackson & Rotevatn, ; Rotevatn, Jackson, Jackson, Tvedt, Bell, & Blækkan, ). Linkage between faults is possible where overlap zones are relatively narrow (Acocella et al, ).…”

“…Linkage between faults is possible where overlap zones are relatively narrow (Acocella et al, 2000). Without a change in the extension vector or an inherited structural grain, this process produces rather straight, or collinear, segmented fault zones as seen both in nature (Acocella et al, 2000;Crider & Pollard, 1998) and in laboratory experiments (Henza et al, 2011;Keep & McClay, 1997;Rotevatn, Jackson, et al, 2018).…”