Lithospheric deformation induced by loading of the Hawaiian Islands and its implications for mantle rheology
Lithospheric deformation induced by loading of the Hawaiian Islands and its implications for mantle rheology
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DOI：
10.1002/2013jb010408
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发表时间：
2013-11-01
影响因子：
3.9
通讯作者：
Watts, A. B.
中科院分区：
文献类型：
--
作者：
Zhong, Shijie;Watts, A. B.
岩石圈的长期流变特性是理解地球表面构造和地幔动力学的基础。在这项研究中，我们建立了三维有限元模型，用于计算岩石圈和地幔的载荷引起的表面变形和应力，并具有真实的非线性粘弹性流变，包括摩擦滑动，低温塑性和高温蠕变。我们测定了夏威夷群岛地区几百万年来火山作用下岩石圈的变形和应力。通过比较模型预测与海洋地壳顶部深度的地震观测和夏威夷群岛地区地震活动性的深度依赖，我们试图限制岩石圈流变。计算表明，载荷引起的表面变形受低温塑性和摩擦滑动控制，但对高温蠕变不敏感。根据实验室推导的低温塑性预测的岩石圈强度需要显著降低，并且需要0.1至0.7之间的摩擦系数(f)来解释观测结果。然而，(f)=0.1对岩石圈浅部的削弱太大，导致应变率和应力的最小值出现在太大的深度，与观测到的地震活动性深度分布不一致。因此，我们的结果表明(f)的值在0.25和0.7之间。最后，根据与观测相匹配的模型，夏威夷群岛下变形岩石圈中积累的最大应力约为100-200MPa，这可能被视为地球上最大的岩石圈应力。
The long-term rheological properties of the lithosphere are fundamental for understanding both surface tectonics and mantle dynamics on Earth. In this study, we have developed 3-D finite element models for computing the load-induced surface deformation and stress for lithosphere and mantle with realistic nonlinear viscoelastic rheology including the frictional sliding, low-temperature plasticity, and high-temperature creep. We have determined the lithospheric deformation and stress due to volcano loading in the Hawaiian Islands region for the last few million years. By comparing model predictions with seismic observations of the depth to the top of oceanic crust and depth dependence of seismicity in the Hawaiian Islands region, we have sought to constrain lithospheric rheology. Our calculations show that the load-induced surface deformation is controlled by low-temperature plasticity and frictional sliding but is insensitive to high-temperature creep. Lithospheric strength predicted from laboratory-derived low-temperature plasticity needs to be reduced significantly, and a frictional coefficient (f) ranging from 0.1 to 0.7 is required in order to account for the observations. However, (f)=0.1 weakens the shallow part of the lithosphere so much that it causes the minima in strain rate and stress to occur at too large depths to be consistent with the observed depth distribution of seismicity. Our results therefore suggest a value for (f) between 0.25 and 0.7. Finally, the maximum stress that accumulates in the deformed lithosphere beneath the Hawaiian Islands is about 100-200MPa for models that match the observations, and this stress may be viewed as the largest lithospheric stress on Earth.