Transient Slow Slip Characteristics of Frictional‐Viscous Subduction Megathrust Shear Zones

The deep roots of subduction megathrusts exhibit aseismic slow slip events, commonly accompanied by tectonic tremor. Observations from exhumed rocks suggest this region the interface is a shear zone with frictional lenses embedded in viscous matrix. Here, we use numerical models to explore transient characteristics finite-width frictional-viscous megathrust zones. Our model utilizes an invariant, continuum-based, regularized form rate- and state-dependent friction (RSF) simulates earthquakes along spontaneously evolving faults 2D heterogeneous continuum. setup includes two elastic plates bounding viscoelastoplastic (subduction melange) inclusions (clasts) varying distributions viscosity contrasts respect surrounding weaker entire exhibits same velocity-weakening RSF parameters, but lower matrix has capacity switch between creep as function local stress state. Results demonstrate mechanism which heterogeneity these zones both (a) sets “speed limit” for earthquake ruptures that nucleate clasts such they propagate at velocities; (b) permits transmission clast clast, allowing substantial distances over domain. For reasonable input modeled events have moment-duration statistics, drops, rupture propagation rates overlap some natural events. These results provide new insights into how geologic observations ancient analogs source may scale up match geophysical constraints on modern phenomena.