A Synthesis of Fracture, Friction and Damage Processes in Earthquake Rupture Zones

Abstract

We review properties and processes of earthquake rupture zones based on field studies, laboratory observations, theoretical models and simulations, with the goal of assessing the possible dominance of different processes in different parts of the rupture and validity of commonly used models. Rupture zones may be divided into front, intermediate, and tail regions that interact to different extents. The rupture front is dominated by fracturing and granulation processes and strong dilatation, producing faulting products that are reworked by subsequent sliding behind. The intermediate region sustains primarily frictional sliding with relatively high slip rates that produce appreciable stress transfer to the propagating front. The tail region further behind is characterized by low slip rates that effectively do not influence the propagating front, although it (and the intermediate region) can spawn small offspring rupture fronts. Wave-mediated stress transfer can also trigger failures ahead of the rupture front. Earthquake ruptures are often spatially discontinuous and intermittent with a hierarchy of asperity and segment sizes that radiate waves with different tensorial compositions and frequency bands. While different deformation processes dominating parts of the rupture zones can be treated effectively with existing constitutive relations, a more appropriate analysis of earthquake processes would require a model that combines aspects of fracture, damage-breakage, and frictional frameworks.

Preparatory Slip in Laboratory Faults: Effects of Roughness and Load Point Velocity

“…Given an average value of K f = 90 MPa/mm measured during stage 5, and G = 30 GPa for La Peyratte granite, Equation 6 gives L c = 39 cm, which exceeds the sample size, suggesting that dynamic slip should not occur. We posit that the discrepancy between L c estimated from Equation 6 and our experimental observations is related to heterogeneous nucleation (Schär et al., 2021), and potentially complex weakening (Ben‐Zion & Dresen, 2022; Paglialunga et al., 2022).…”

How Do Earthquakes Stop? Insights From a Minimal Model of Frictional Rupture

“…As shown in Figure 1b, the one‐dimensional model under imposed‐displacement boundary conditions can describe the response of a low velocity fault zone that is much more compliant than the surrounding wall rock. In natural systems, the damage, plasticity and compliance of the low velocity fault zone are expected to evolve both spatially along the fault according to the gradient in fault maturity (Cappa et al., 2014), but also temporally as a dynamic result of the rupture (Ben‐Zion & Dresen, 2022; Mia et al., 2022). The proposed model can be extended to account for finite contrast of compliance between the damage zone and the wall rock, for instance by including a viscous term $$\bar{\nu }\dot{\bar{u}}$$ on the right hand side of Equation 1 to account for radiation damping effects, that is, mechanical energy lost as elastic waves in the surrounding bulk (Barras et al., 2019).…”

On catching the preparatory phase of damaging earthquakes: an example from central Italy

“…The increasing availability of catalogs properly populated by microearthquakes, especially along deep transition zones of megathrusts, or acoustic emissions in case of laboratory stick-slip experiments, is pushing the scienti c community in mining data across wide spatio-temporal scales, from which it emerges that the spatio-temporal evolution of microseismicity/acoustic emissions provide information on seismic friction and coupling. The latter pieces of information resulted useful to predict in machinelearning studies the occurrence time of laboratory earthquakes, seismic tremor, and slow slip events [47][48][49][50][51].…”