Subduction earthquake sequences in a non-linear visco-elasto-plastic megathrust

Luca Dal Zilio, Nadia Lapusta, Jean-Philippe Avouac, Taras Gerya

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Abstract

We present a 2-D thermomechanical computational framework for simulating earthquake sequences in a non-linear visco-elasto-plastic compressible medium. The method is developed for a plane-strain problem and incorporates an invariant formulation of the classical rateand state-dependent friction law and an adaptive time-stepping, which allows the time step to vary by many orders of magnitude during a simulation. Long-term tectonic convergence is
imposed by displacing a boundary at a constant rate, whereas temperature-dependent viscosity is solved using a rapidly converging Newton–Raphson scheme. The 2-D volume is discretized using finite differences on a fully staggered grid and marker-in-cell techniques. An adaptive free-surface approximation is used to modulate the air viscosity with the time step, which allows stresses to vanish on the free surface during the propagation of fast slipping events. We present a set of increasingly complex models in which we investigate how inertia, radiation damping, thermally activated non-linear rheology and off-megathrust splay-fault events affect sequences ofseismic and aseismic slip on a simplified subduction megathrust. The new method
provides a unique computational framework to analyse earthquake sequences and to connect forearc deformation with the dynamic properties of the megathrust, thus providing a physical link between observations spanning from slow interseismic strain accumulation to localized coseismic slip of individual earthquakes and post-seismic viscoelastic relaxation.
Original languageEnglish
Pages (from-to)1098-1121
Number of pages24
JournalGeophysical Journal International
Volume229
Issue number2
Early online date27 Dec 2021
DOIs
Publication statusPublished - 1 May 2022

Bibliographical note

We thank Casper Pranger, Robert Herrendorfer, Camilla Penney, Sylvain Barbot, Valére Lambert and Whitney Behr for discussions. This research was supported by the Swiss National Science Foundation (SNSF) (grants No. P2EZP2 184307 and P400P2 199295 ), the United States Geological Survey (USGS) Earthquake Hazard Program (grant No. GP21AP10037 ) and by the Cecil & Sally Drinkward postdoctoral fellowship of the Department of Mechanical and Civil Engineering at the California Institute of Technology. Numerical simulations were performed on ETH cluster Euler. We thank the Editor Margarita Segou, Duo Li and an anonymous reviewers for providing insightful comments that helped to improve the quality of this paper.

This article has been accepted for publication in Geophysical Journal International ©: 2021 Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.

Keywords

  • Earthquake dynamics
  • Numerical modelling
  • Seismicity and tectonics
  • Subduction zone processes
  • Rehology and friction of fault zones
  • Rheology and friction of fault zones

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