Abstract

AbstractTaking the full complexity of subduction zones into account is important for realistic modeling and hazard assessment of subduction zone seismicity and associated tsunamis. Studying seismicity requires numerical methods that span a large range of spatial and temporal scales. We present the first coupled framework that resolves subduction dynamics over millions of years and earthquake dynamics down to fractions of a second. Using a two‐dimensional geodynamic seismic cycle (SC) model, we model 4 million years of subduction followed by cycles of spontaneous megathrust events. At the initiation of one such SC event, we export the self‐consistent fault and surface geometry, fault stress and strength, and heterogeneous material properties to a dynamic rupture (DR) model. Coupling leads to spontaneous dynamic rupture nucleation, propagation, and arrest with the same spatial characteristics as in the SC model. It also results in a similar material‐dependent stress drop, although dynamic slip is significantly larger. The DR event shows a high degree of complexity, featuring various rupture styles and speeds, precursory phases, and fault reactivation. Compared to a coupled model with homogeneous material properties, accounting for realistic lithological contrasts doubles the amount of maximum slip, introduces local pulse‐like rupture episodes, and relocates the peak slip from near the downdip limit of the seismogenic zone to the updip limit. When an SC splay fault is included in the DR model, the rupture prefers the splay over the shallow megathrust, although wave reflections do activate the megathrust afterward.

Highlights

  • Throughout the past decades, enigmatic observations of subduction zone earthquakes have repeatedly given rise to new insights

  • We describe the results from the seismic cycle (SC) event and the corresponding dynamic rupture (DR) rupture in detail and compare them

  • By coupling a geodynamic seismic cycle model to a dynamic rupture model, we successfully model the geodynamic evolution of a subduction zone down to a single dynamic earthquake rupture of the megathrust

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Summary

Introduction

Throughout the past decades, enigmatic observations of subduction zone earthquakes have repeatedly given rise to new insights. Large slip occurring up to the trench during the 2011 Mw9.0 Tōhoku‐Oki earthquake demonstrated how poorly the occurrence of slip in shallow, presumably velocity‐strengthening regions is understood to date (Fujiwara et al, 2011; Lay et al, 2011). Understanding the seismic characteristics along megathrusts from the trench to the downdip limit of the seismogenic zone is crucial for improving the assessment of seismic—and the associated tsunami—hazards. The physics governing subduction zone seismicity occurs on a wide range of temporal scales. Capturing the relevant physics across these time scales is computationally and numerically challenging and currently not yet feasible within a single modeling framework

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