Asthenosphere flow modulated by megathrust earthquake cycles
Date of Issue2018
Earth Observatory of Singapore
Subduction megathrusts develop the largest earthquakes, often close to large populationcenters. Understanding the dynamics of deformation at subduction zones is therefore important to betterassess seismic hazards. Here I develop consistent earthquake cycle simulations that incorporate localizedand distributed deformation based on laboratory-derived constitutive laws by combining boundary andvolume elements to represent the mechanical coupling between megathrust slip and solid-state flow in theoceanic asthenosphere and in the mantle wedge. The model is simplified, in two dimensions, but may helpthe interpretation of geodetic data. Megathrust earthquakes and slow-slip events modulate the strain ratein the upper mantle, leading to large variations of effective viscosity in space and time and a complexpattern of surface deformation. While fault slipand flow in the mantle wedge generate surfacedisplacements in the same, that is, seaward, direction, the viscoelastic relaxation in the oceanicasthenosphere generates transient surface deformation in the opposite, that is, landward, directionabove the rupture area of the mainshock. Aseismic deformation above the seismogenic zone may bechallenging to record, but it may reveal important constraints about the rheology of the subducting plate.
Geophysical Research Letters
© 2018 The Authors. This is an open access article under the terms of the Creative Commons Attribution-Non Commercial-No Derivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.