Duo Li , Alice-Agnes Gabriel 

Slow slip events (SSEs) have been observed in spatial and temporal proximity to megathrust earthquakes in various subduction zones, including the 2014 $M_\mathrm{w}$7.3 Guerrero, Mexico earthquake which was preceded by a $M_\mathrm{w}$ 7.6 SSE. However, the underlying physics connecting SSEs to earthquakes remains elusive. Here, we link 3D slow-slip cycle models with dynamic rupture simulations across the geometrically complex flat-slab Cocos plate boundary. Our physics-based models reproduce key regional geodetic and teleseismic fault slip observations on timescales from decades to seconds.
We find that accelerating SSE fronts transiently increase shear stress at the down-dip end of the seismogenic zone, modulated by the complex geometry beneath the Guerrero segment. The shear stresses cast by the migrating fronts of the 2014 $M_\mathrm{w}$ 7.6 SSE are significantly larger than those during the three previous episodic SSEs that occurred along the same portion of the megathrust. We show that the transient stresses caused by this SSE are large enough to nucleate earthquake dynamic rupture. However, additional frictional asperities in the seismogenic part of the megathrust are required to explain the observed complexities in the coseismic energy release and static surface displacements of the 2014 $M_\mathrm{w}$7.3 Guerrero earthquake. We conclude that it is crucial to jointly analyze the long- and short-term interactions and complexities of SSEs and megathrust earthquakes across several (a)seismic cycles accounting for megathrust geometry. Our study has important implications for identifying earthquake precursors and understanding the link between transient and sudden megathrust faulting processes.