Revisiting viscoelastic effects on interseismic deformation and locking degree: A case study of the Peru-North Chile subduction zone
Revisiting viscoelastic effects on interseismic deformation and locking degree: A case study of the Peru-North Chile subduction zone
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DOI：
10.1002/2015jb011903
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发表时间：
2015-06-01
影响因子：
3.9
通讯作者：
Oncken, Onno
中科院分区：
文献类型：
--
作者：
Li, Shaoyang;Moreno, Marcos;Oncken, Onno
在俯冲带地震周期的所有阶段，粘弹性效应都可能发挥重要作用。然而，目前的大多数模型忽略了震间变形模式中的这种影响。在这里，我们使用有限元模型来研究粘弹性对震间变形的控制，并强调用纯弹性模型解释正反问题数据的缺陷。我们的结果证实，弹性模型容易高估震间锁定深度，这是估计最大可能地震震级的关键参数。粘弹性模型的应用提高了对地震间变形的拟合度，特别是在内陆地区。此外，我们建立了受地球物理和GPS数据约束的三维有限元模型，并将我们的方法应用于秘鲁-智利北部俯冲带。我们的结果表明，粘弹性效应对GPS观测数据的贡献很大。在弹性模型中解释为弧后缩短的信号也可以用粘弹性变形来解释，这反过来又极大地细化了倾角和走向方向的震间锁定模式。我们的粘弹性锁定图与前几次地震，特别是最近的2014年8.1级伊基克地震的滑移分布显示出很好的相关性。不正确的弹性假设影响了关于滑动赤字计算的地震间变形分析。因此，我们的结果表明，有必要彻底重新评估现有的基于纯弹性模型的锁定模型，其中一些模型将粘弹性变形归因于不同的来源，如微板条运动。
Viscoelastic effects potentially play an important role during all phases of the earthquake cycle in subduction zones. However, most current models neglect such effects in the interseismic deformation pattern. Here we use finite element method (FEM) models to investigate the control of viscoelasticity on interseismic deformation and to highlight the pitfalls of interpreting the data with purely elastic models for both the forward and inverse problems. Our results confirm that elastic models are prone to overestimating the interseismic locking depth, a crucial parameter for estimating the maximum possible earthquake magnitude. The application of the viscoelastic model improves the fit to the interseismic deformation, especially in the inland area. Additionally, we construct 3-D FEM models constrained by geophysical and GPS data and apply our methodology to the Peru-North Chile subduction zone. Our results indicate that viscoelastic effects contribute significantly to the observed GPS data. The signals interpreted as back-arc shortening in the elastic model can be alternatively explained by viscoelastic deformation, which, in turn, dramatically refines the interseismic locking pattern in both dip and strike directions. Our viscoelastic locking map exhibits excellent correlation with the slip distributions of previous earthquakes, especially the recent 2014 Mw 8.1 Iquique earthquake. The incorrect elastic assumptions affect the analysis of interseismic deformation with respect to slip deficit calculations. Our results thus suggest that it is necessary to thoroughly reevaluate existing locking models that are based on purely elastic models, some of which attribute viscoelastic deformation to different sources such as microplate sliver motions.