摘要
An improved understanding of postseismic crustal deformation following large subduction earthquakes may help to better understand the rheological properties of upper mantle and the slip behavior of subduction interface.Here we construct a three-dimensional viscoelastic finite element model to study the postseismic deformation of the 2014 M_(W)8.1 Iquique,Chile earthquake.Elastic units in the model include the subducting slab,continental and oceanic lithospheres.Rheological units include the mantle wedge,the oceanic asthenosphere and upper mantle.We use a 2 km thick weak shear zone attached to the subduction fault to simulate the time-dependent stress-driven afterslip.The viscoelastic relaxation in the rheological units is represented by the Burgers rheology.We carry out grid-searches on the shear zone viscosity,thickness and viscosity of the asthenosphere,and they are determined to be 10^(17)Pa s,110 km and 2×10^(18)Pa s,respectively.The stress-driven afterlsip within the first two years is up to~47 cm and becomes negligible after two years(no more than 5 cm/yr).Our results suggest that a thin,low-viscosity oceanic asthenosphere together with a weak shear zone attached to the fault are required to better reproduce the observed postseismic deformation.
基金
This work was supported by the National Key R&D Program(2018YFC504103)
Strategic Priority Research Program of Chinese Academy of Sciences(XDA20070302)
the National Natural Science Foundation of China(41774109).
