Nonlinear fault damage zone scaling revealed through analog modeling

Abstract

Fault damage zones strongly influence fluid flow and seismogenic behavior of faults and are thought to scale linearly with fault displacement until reaching a threshold thickness. Using analog modeling with different frictional layer thicknesses, we investigate damage zone dynamic evolution during normal fault growth. We show that experimental damage zone growth with displacement is not linear but progressively tends toward a threshold thickness, being larger in the thicker models. This threshold thickness increases significantly at fault segment relay zones. As the thickness threshold is approached, the failure mode progressively transitions from dilational shear to isochoric shear. This process affects the whole layer thickness and develops as a consequence of fault segment linkage as inferred in nature when the fault matures. These findings suggest that fault damage zone widths are limited both by different scales of mechanical unit thickness and the evolution of failure modes, ultimately controlled in nature by lithology and deformation conditions.

Analogue modelling of basin inversion: a review and future perspectives

“…By contrast, materials such as micas and micro-beads have a significant lower angle of internal friction and deform more readily. Weaker mica layers are used to facilitate interlayer slip, while conveniently creating visible layering in sections as well (McClay, 1989(McClay, , 1996McClay, 1991, 1992, see Sect. 3.6), whereas micro-beads have been used to simulate basal detachment layers (Panien et al, 2006a).…”

“…This rubber sheet is generally inserted between two base plates (Amilibia et al, 2005;Dooley and Hudec, 2020;Yu et al, 2021) (Fig. 5h), even though some authors have also used a rubber sheet covering the full length of the model (McClay, 1989). By pulling apart the base plates or sidewalls between which the rubber is fixed, the rubber is stretched and creates a distributed type of deformation at the model base, rather than the highly localized deformation induced by a VD (Vendeville et al, 1987;Withjack and Jamison, 1986;McClay, 1990;McClay et al, 2002;Corti et al, 2007;Henza et al, 2010Henza et al, , 2011Zwaan et al, 2019).…”

“…Amilibia et al, 2005). Note that the rubber sheet may also cover the whole base of the model (McClay, 1989). (i) Foam base set-up (e.g.…”

“…In addition to top-view photography, model set-ups with transparent sidewalls enable direct monitoring of model deformation at the sides of the experiment (Koopman et al, 1987;McClay, 1989McClay, , 1995Buchanan and McClay, 1992;McClay and Buchanan, 1992;Gomes et al, 2006Gomes et al, , 2010Jagger and McClay, 2016;Lebinson et al, 2020, Fig. 7b).…”

“…Similar to the mobile basement set-ups, fixed rigid basement (footwall) block set-ups have been used for some of the earliest basin inversion models (McClay, 1989(McClay, , 1995Mitra, 1993;Mitra and Islam, 1994;Buchanan and McClay, 1991). These set-ups primarily serve to study basin inversion as a 2D process with orthogonal extension followed by orthogonal compression (Figs.…”