Physical, Analytical, and Numerical Modeling of Reverse Fault Displacement through Near Surface Soils

Variable fault tip propagation rates affected by near-surface lithology and implications for fault displacement hazard assessment

“…We thus assumed that upward fault tip propagation rate experienced a significant shift: the proposed twostage model fits well with the stratigraphy, implying that this behavior is strictly dependent on the geo-mechanical properties of the cut lithologies and on the underlying stratigraphy. The temporal analysis of fault growth history ( Mechanical properties of the ruptured materials strongly influence strain localization and amount of slip at surface, as observed following large earthquakes (Tchalenko & Ambraseys, 1970;Irvine & Hill, 1993;Lazarte et al, 1994;Johnson et al, 1997;Bray & Kelson, 2006;Fletcher et al, 2014;Teran et al, 2015;Floyd et al, 2016;Livio et al, 2016) or resulting from numerical and analogue modeling (Cole & Lade, 1984;Bray et al, 1994;Johnson & Johnson, 2002a;Cardozo et al, 2003;Moss et al, 2018). In particular, fault propagation rate is dependent on axial strain failure of soils (Bray et al, 1994), Young's modulus and dilation angle (Lin et al, 2006) or on viscosity coefficient, if material is approximated according to a viscous folding theory (Johnson & Johnson, 2002a).…”

“…Overburden thickness, as well, strongly influences fault zone width and fabric at surface, resulting in different amount of slip on single fault strands (Tchalenko, 1970;Horsfield, 1977;Bray et al, 1994;Schlische et al, 2002;Quigley et al, 2012;Zinke et al, 2014;Teran et al, 2015;Floyd et al, 2016). For a recent review of the literature on this issue the reader is referred Moss et al (2018).…”

“…Our results, derived from a purely kinematic approach, confirm that: i) if geologically constrained, trishear kinematic models can be considered good analogues for mechanical models, with the advantage of being independent from geotechnical parameters (e.g., Cardozo et al, 2003); ii) P/S is the most affecting parameter, driving the output of a trishear model (Allmendinger and Shaw, 2000), which can be considered as the resultant of a combination of several mechanical and geotechnical characteristics of the cut lithologies (i.e., cohesion, water content, grain-size distribution etc.). The P/S values measured on several analogue models and using loose to dense sand, range from 5 to 50 (Cole & Lade, 1984;Bray et al, 1994;Anastosopoulos et al, 2007;Bransby et al, 2008;Moss et al, 2018), thus suggesting that these experimental materials are not perfectly scaled for large scale experiments of a near surface faulting prototype. Finite element modeling of reverse faulting through loose to stiff soils (Moss et al 2018), obtained P/S values between 0.4 and 2.…”

“…The P/S values measured on several analogue models and using loose to dense sand, range from 5 to 50 (Cole & Lade, 1984;Bray et al, 1994;Anastosopoulos et al, 2007;Bransby et al, 2008;Moss et al, 2018), thus suggesting that these experimental materials are not perfectly scaled for large scale experiments of a near surface faulting prototype. Finite element modeling of reverse faulting through loose to stiff soils (Moss et al 2018), obtained P/S values between 0.4 and 2. Recently, also Moss et al (2013) came to a similar result, considering a geophysically-derived parameter for soil shear stiffness, as a synthetic descriptor for these characteristics.…”

“…Nevertheless, surface faulting can result in a narrow and discrete rupture zone, rather than in a broader and more distributed one, where folding is predominant: the so-called fault-zone fabric (e.g., Teran et al, 2015). The mode of fault propagation toward the surface has been recently investigated through numerical and analogue approaches (Moss et al, 2013(Moss et al, , 2018Thebian et al, 2018) providing insights on some of the most important parameters affecting surface faulting. Some of these parameters that control fault zone fabric are related to the characteristics of near-surface geology (i.e., lithology, overburden thickness, and water content; see Teran et al, 2015 for a review).…”