Rheological Transitions Facilitate Fault‐Spanning Ruptures on Seismically Active and Creeping Faults

Abstract

Physical constraints on the seismogenic potential of major fault zones may aid in improving seismic hazard assessments, but the mechanics of earthquake nucleation and rupture are obscured by the complexity that faults display. In this work, we investigate the mechanisms behind giant earthquakes by employing a microphysically based seismic cycle simulator. This microphysical approach is directly based on the mechanics of friction as inferred from laboratory tests and can explain a broad spectrum of fault slip behavior. We show that regular earthquakes are controlled by the size and distribution of (nominally) frictionally unstable asperities, whereas fault‐spanning earthquakes are governed by a rheological transition occurring in creeping fault segments. Moreover, this facilitates the nucleation of giant earthquakes on faults that are weakly seismically coupled (i.e., creeping). This microphysically based approach offers opportunities for investigating long‐term seismic cycle behavior of natural faults.

Intermittent Slip Along the Alto Tiberina Low‐Angle Normal Fault in Central Italy

“…Third, since the ATF also shows a high degree of tectonic coupling with its main antithetic faults, it is likely that microseismicity and aseismic slip on ATF may control the seismic activity on the shallower splays. This ATF specific behavior can be retrieved in other tectonic environments (e.g., Harris, 2017), in laboratory experiments (e.g., Collettini et al, 2011) and in numerical simulations (e.g., van den Ende et al, 2020) and confirm the recent evidence about the control of seismicity by complex fault systems (e.g., Ross et al, 2020). A better understanding of the interplay of the seismic activity within complex fault systems, including segments undergoing both Geophysical Research Letters 10.1029/2020GL089039 creeping and fast/slow slip earthquakes, seems to be the main road to provide better earthquake hazard characterizations (e.g., Avouac, 2015;Bürgmann, 2018).…”

Microphysical Modeling of Carbonate Fault Friction at Slip Rates Spanning the Full Seismic Cycle

“…This extended CNS model, in combination with our earlier effort in bridging the very-LV range (J. Chen, Niemeijer, & Spiers, 2017;J. Chen et al, 2020), now covers the full spectrum of slip velocities from earthquake nucleation to seismic slip rates (Figure 4).…”

“…This yields the following equations for shear and normal (compaction) strain rates by thermally activated deformation mechanisms (cf., Equation 1b, see also J. Chen et al, 2020):…”

Microphysical modeling of carbonate fault friction at slip rates spanning the full seismic cycle

“…By analogy with the frictional healing effect caused by compaction achieved during a pause in slip, that is, during the hold period of a slide-hold-slide experiment, Equation 17b of J. Chen et al (2020) can be used to estimate the maximum strength gained due to compaction in the interval V c < V < V w , that is, prior to the onset of weakening at V ≈ V w : CHEN ET AL. where  is the instantaneous porosity at the peak strength.…”