Journal Article

Linking 3D Long‐Term Slow‐Slip Cycle Models With Rupture Dynamics: The Nucleation of the 2014 Mw 7.3 Guerrero, Mexico Earthquake

Gabriel, Alice‐Agnes, Li, Duo

2024

Overview

Slow slip events (SSEs) have been observed in spatial and temporal proximity to megathrust earthquakes in various subduction zones, including the 2014 Mw 7.3 Guerrero, Mexico earthquake which was preceded by a Mw 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 Mw 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 SSE transient stresses are large enough to nucleate earthquake dynamic rupture and affect rupture dynamics. 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 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. Plain Language Summary The 2014 Mw 7.3 Guerrero, Mexico earthquake was preceded by an Mw 7.6 slow slip event (SSE), a transient of aseismic fault slip, which offers a valuable opportunity to explore the relationship between slow slip and major subduction earthquakes. By modeling both long‐term cycles of slow slip events and dynamic earthquake rupture, we reproduce various measurements from geodetic surveys and seismic recordings. We find that as the migrating front of the 2014 SSE accelerated, it caused additional loading at depth where the earthquake occurred. In this case, the stress levels of the preceding 2014 SSE were notably higher than previous SSEs which appeared in the same fault portion between 2001 and 2014, and may have contributed to initiating the earthquake. Additionally, we find that variations in friction across the megathrust affect the complexity of energy release and surface displacements during the earthquake. By examining the temporary and long‐term interactions between SSEs and earthquakes, we gain important insights into potential earthquake precursors and the processes involved in how faults move. This research holds significant implications for enhancing our understanding of how large earthquakes occur in subduction zones. Key Points We present the first 3D linked models of dynamic earthquake rupture and long‐term slow slip cycles along the flat‐slab Cocos plate The modeled long‐term slow slip cycles and earthquake dynamic rupture capture key observations on timescales from decades to seconds The transient stress evolution of the long‐term slow slip cycles may have initiated the 2014 Mw 7.3 Guerrero, Mexico earthquake

• Publisher: John Wiley & Sons, Inc,Wiley
• Subject: earthquake initiation / Earthquakes / Fault lines / Geometry / megathrust earthquake / Physics / physics‐based numerical modeling / Seismic activity / Shear stress / slow slip cycles