The Minimum Scale of Grooving on a Recently Ruptured Limestone Fault

Abstract

Faults have grooves that are formed by abrasion and wear during slip. Recent observations indicate that this grooving is only a large‐scale feature, indicating brittle behavior has a length scale limit. The connection between this scale and earthquake behavior remains limited because no examples exist from a proven seismogenic fault. Here, we address this problem and analyze differences in this scale between lithologies to further our understanding of the underlying mechanics. This study uses samples from the Mt. Vettoretto fault collected after the Norcia earthquake of 2016. We imaged fault topography with a white light interferometer and 10 μm resolution structure from motion and then calculated a Monte Carlo version of root mean square roughness. We found a minimum scale of grooving of ~100 μm. In comparing this fault to the Corona Heights fault, we find that this minimum grooving scale is consistent with predictions based on material properties.

Microstructural Controls on Mixed Mode Dynamic Fracture Propagation in Crystalline and Porous Granular Rocks

“…These rocks display different failure mechanisms due to variations in cohesive strength and ability to alleviate stress concentration through yielding and grain crushing (e.g., Rück et al, 2017;Vora & Morgan, 2019). Understanding how mixed mode dynamic fracture propagation manifests in these rock types is critically important in understanding the development of seismogenic fault damage zones, which exert fundamental controls on coseismic energy dissipation, interseismic strain energy accumulation, and the longer-term hydraulic structure of fault zones (e.g., Aben et al, 2017;Faulkner et al, 2011;Okubo et al, 2019;Xia & Rosakis, 2021), the preferential pulverization of crystalline over granular rocks in these damage zones (e.g., Aben et al, 2017;Dor et al, 2006;Mitchell et al, 2011), and surface roughness related to crack growth (e.g., Okamoto et al, 2019;Renard et al, 2012;Schmittbuhl et al, 1993). These brittle damage processes also have implications for engineering applications involving fracture propagation such as hydraulic fracturing (e.g., Antinao Fuentealba et al, 2020), stability of underground openings (e.g., Zhao et al, 2010), damage and seismic radiation from underground explosions (e.g., Sammis, 2011) and allow us to evaluate assumptions regarding the evolution of fracture properties used in micromechanical models of failure in polycrystalline materials (Ashby & Sammis, 1990;Bhat et al, 2012).…”

The impact of weathering upon the roughness characteristics of a splay of the active fault system responsible for the massive 2016 seismic sequence of the Central Apennines, Italy

“…Previous studies on natural faults have documented self-affine behavior with two distinct scaling transformations along the direction of slip and perpendicularly to it (Mandelbrot, 1985;Power and Tullis, 1991;Schmittbuhl et al, 1993;Candela et al, 2009). This self-affinity has been more recently quantified over several length scales, with an overall H perp /H slip ratio of ∼1.33 (e.g., Candela et al, 2012;Renard et al, 2013), which terminates at the micrometer-scale where a transition to an isotropic scaling roughness occurs (Siman-Tov et al, 2013; Candela and Brodsky, 2016;Okamoto et al, 2019). The fault studied in this work is, however, quite isotropic in origin as shown by the clustering around 1 of both H perp /H slip and a perp /a slip for Zone 2, which is the least weathered and most recently uncovered zone.…”

“…For lab-based studies, high-accuracy laser profilom-eters, white light interferometers, and atomic force microscopes have facilitated the investigation of fault asperities from centimeter down to nanometer scales (e.g., Candela et al, 2009;Siman-Tov et al, 2013;Renard et al, 2013;. More recently, structure from motion-multiview stereo (SfM-MVS) photogrammetry has been applied to the characterization of fault roughness (e.g., Corradetti et al, 2017;Olkowicz et al, 2019;Zambrano et al, 2019;Okamoto et al, 2019), which carries the advantage of being highly scalable while only requiring a consumer-grade camera for data acquisition.…”

“…Vettore fault system in the Central Apennines, Italy. The area has been subjected to historical and recent seismicity (Tondi and Cello, 2003), and since the seismic crises of 2016 that exposed several wide, fresh portions of the fault, it has become the focus of numerous studies relating to seismogenic faults (e.g., Smeraglia et al, 2017;Okamoto et al, 2019).…”

A microphysical model of rock friction and the brittle-ductile transition controlled by dislocation glide and backstress evolution

“…Assuming that the thickness X over which deformation is accommodated is equal to the diameter of the largest plastically deforming asperities (i.e., the deformation is accommodated in a hemisphere, which is the asperity), we can relate the sliding strain rate to the largest asperity size L (which is thought to correspond to the variable Dc), although we do not explicitly make this assumption a priori. However, it is an appealing possibility because Dc has been suggested to be a length scale that demarcates the transition from plastic deformation to brittle mechanisms (Candela & Brodsky, 2016), and variations in Dc can be predicted from material properties (Okamoto et al, 2019). Furthermore, as we will demonstrate below, a length scale related to the size of the deforming region emerges naturally from 'strain-gradient plasticity' theory (e.g., Nix & Gao, 1998).…”