Mainshock and Aftershock Sequence Simulation in Geometrically Complex Fault Zones

Abstract

The complexity of natural fault zones has been a target of numerous studies (Ben-Zion & Sammis, 2003; Faulkner et al., 2010). Although often simplified as a single flat surface in modeling, natural faults have complicated geometry. Faults are typically composed of a few discontinuous segments at a wide range of scales (Manighetti et al., 2015; Segall & Pollard, 1980). Each continuous slip surface has deviation from planarity over broad spatial scales. The fractal-like geometrical irregularity of fault surfaces is referred to as fault roughness and is documented from various observations (

Impact Versus Frictional Earthquake Models for High‐Frequency Radiation in Complex Fault Zones

“…There are a number of other earthquake rupture models that are distinct from or modified from the standard rough fault frictional paradigm described above. For example, other studies have examined the role of a low-velocity fault zone (e.g., Huang et al, 2014Huang et al, , 2016, creation of damage during rupture (e.g., Lyakhovsky & Ben-Zion, 2020;Okubo et al, 2019;Xu et al, 2015), and the effects of including off-fault fractures or short branches (e.g., Ma & Elbanna, 2019;Okubo et al, 2019;Ozawa & Ando, 2021). We recognize that these other models include different assumptions (which may or may not include viscoplasticity) and make different predictions from the rough fault frictional models that we compare with the impact model.…”

Hindcasting injection-induced aseismic slip and microseismicity at the Cooper Basin Enhanced Geothermal Systems Project

“…We assume negligible stress interactions between secondary faults, which is justified when fault dimensions are small compared to distances between faults 24 . We also neglect stress perturbation feedback onto the main fault from the off-fault seismicity, which is supported by numerical experiments showing negligible elastic stress transfer from off-fault aftershocks to the main fault in a similar modeling study 25 . The last two assumptions allow for the efficient simulation of hundreds of microseismic events.…”

“…Third, in-situ and laboratory experiments indicate that pressurized, water-saturated fault gouge tends to be velocity-strengthening when slipping 9 . Seismic observations at tectonic faults 38 and numerical experiments 25 show an abundance of off-fault aftershocks, suggesting that secondary faults surrounding the main fault tend to be velocity-weakening.…”

Hindcasting injection-induced aseismic slip and microseismicity at the Cooper Basin Enhanced Geothermal Systems Project

“…We assume negligible stress interactions between secondary faults, which is justified when fault dimensions are small compared to distances between faults 26 . We also neglect stress perturbation feedback onto the main fault from the off-fault seismicity, which is supported by numerical experiments showing negligible elastic stress transfer from off-fault aftershocks to the main fault in a similar modeling study 27 . The last two assumptions allow for the efficient simulation of hundreds of microseismic events ( Methods ).…”