Viscoelastic relaxation following subduction earthquakes and its effects on afterslip determination
Viscoelastic relaxation following subduction earthquakes and its effects on afterslip determination
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DOI：
10.1002/2014jb011707
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发表时间：
2015-02-01
影响因子：
3.9
通讯作者：
Wang, Kelin
中科院分区：
文献类型：
--
作者：
Sun, Tianhaozhe;Wang, Kelin
余滑通常被认为是大地震后立即震后变形的控制过程，通常是根据纯弹性模型的大地测量结果推断出来的。然而，2011年东北9级地震后，观测到的海沟附近地区的运动反转表明，同震应力的粘弹性松弛占主导地位。为了了解粘弹性在确定余滑中的重要性，我们采用双粘性Burgers地幔流变学，并使用有限元模型来探索短期震后变形中的粘弹性松弛是如何受各种几何和流变因素控制的。我们的结果表明，在大地震(M-W>；8.0)发生后，粘弹性形变总是会引起内陆和海沟地区的反向运动和破裂端附近的下沉，尽管这种震后运动的速度取决于当地的条件，如板块的年龄和厚度以及瞬变的地幔粘性值。而弹性模型可能足以用于M-W地震的余滑估计
Afterslip is commonly thought to be the controlling process in postseismic deformation immediately following a great megathrust earthquake and is usually inferred from geodetic observations using purely elastic models. However, observed motion reversal of the near-trench area right after the 2011 M-w 9 Tohoku-oki earthquake demonstrates the dominance of viscoelastic relaxation of coseismically induced stresses. To understand the importance of incorporating viscoelasticity in afterslip determination, we employ biviscous Burgers mantle rheology and use finite element models to explore how viscoelastic relaxation in short-term postseismic deformation is controlled by various geometrical and rheological factors. Our results indicate that immediately after large megathrust earthquakes (M-w>8.0), viscoelastic deformation should always cause opposing motion of inland and trench areas and subsidence around landward termination of the rupture, although the rate of such postseismic motion depends on local conditions such as the age and hence thickness of the slab and transient mantle viscosity values. While elastic models may be adequate for afterslip estimation for earthquakes of M-w