Spectral-finite element approach to viscoelastic relaxation in a spherical compressible Earth: application to GIA modelling
Spectral-finite element approach to viscoelastic relaxation in a spherical compressible Earth: application to GIA modelling
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DOI：
10.1111/j.1365-246x.2010.04854.x
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发表时间：
2011
影响因子：
2.8
通讯作者：
Yoshiyuki Tanaka;V. Klemann;Z. Martinec;R. Riva
中科院分区：
文献类型：
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作者：
Yoshiyuki Tanaka;V. Klemann;Z. Martinec;R. Riva
冰后反弹物理模型的选择对于从观测数据中获取有关地幔流变性和粘性的信息起着决定性的作用。在地幔流变学模型中，尽管地震观测表明地幔是由可压缩物质组成的，但通常假定是不可压缩的麦克斯韦物质。在这项研究中，为了评估可压缩性对冰川均衡调整(GIA)的影响，将Martinec提出的谱-有限元方法扩展到考虑可压缩性的影响。用该方法计算了Peltier的ICE5G/VM2地球模型/冰川-历史组合的现今速度场，考虑了Hagehoorn等人公式中的海平面方程。结果表明，压缩系数对竖向位移速率的影响不大，而水平位移速率显着增大。例如，当考虑可压缩性时，Fennoscandia和Laurentide周围的速率会变得两倍。可压缩模型和不可压缩模型之间的这种巨大差异可以通过调整不可压缩模型的弹性刚度来减小，从而使抗弯刚度与可压缩模型中的弯曲刚度大致相同。然而，对于超过8000公里的波长，∼1 mm yr−1的差异仍然存在。这些结果表明，在模拟GIA引起的水平运动时，压缩性的影响是不能忽略的。
SUMMARY The choice of the physical model of postglacial rebound plays a decisive role to derive information about the mantle rheology and viscosity from observed data. In models for the mantle rheology, an incompressible Maxwell material is often assumed in spite of seismic observations showing that the Earth's mantle is composed of compressible material. In this study, in order to assess the influence of compressibility on glacial isostatic adjustment (GIA), the spectral-finite element approach proposed by Martinec is extended to incorporate the effect of compressibility. Using this approach, the present-day velocity field is computed for Peltier's ICE5G/VM2 earth-model/glaciation-history combination considering the sea level equation in the formulation of Hagedoorn et al. The results show that the effect of compressibility on the vertical displacement rate is small whereas the horizontal rates are markedly enhanced. For example, the rate around Fennoscandia and Laurentide becomes twice as large when compressibility is considered. This large difference between the compressible and incompressible models can be reduced by adjusting the elastic rigidity of the incompressible model so that the flexural rigidity becomes approximately the same as that in the compressible model. However, differences of ∼1 mm yr−1 still remain for wavelengths longer than 8000 km. These findings show that when modelling horizontal motion induced by GIA, the influence of compressibility cannot be neglected.