| 利用黏弹性有限元模型研究挪威北海北部地区末次冰期以来的冰后回弹和应力演化 |
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| 引用本文： | 孟秋,胡才博,石耀霖.利用黏弹性有限元模型研究挪威北海北部地区末次冰期以来的冰后回弹和应力演化[J].地球物理学报,1954,63(10):3751-3763. |
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| 作者姓名： | 孟秋 胡才博 石耀霖 |
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| 作者单位： | 中国科学院大学地球与行星科学学院, 中国科学院计算地球动力学重点实验室, 北京 100049 |
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| 基金项目： | 国家重点研发计划"地球系统模式的改进、应用开发和高性能计算"子课题"大气、海洋、陆面、海冰及陆冰模式及其耦合技术与方法应用软件"（2016YFB0200801），国家重点研发计划"华北克拉通成矿系统的深部过程与成矿机理"子课题"胶辽地区岩石圈深部结构"（2016YFC0600101）联合资助. |
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| 摘 要： | 挪威北海北部在末次冰期存在较大范围的冰盖，其冰盖的加载和卸载会对地表变形和内部应力调整产生重要影响.本文基于Maxwell黏弹性本构关系，根据初应力法自主开发了一套Maxwell黏弹性体有限元程序，它可以考虑重力和构造加载、地球介质弹性的纵向和横向不均匀性以及黏性的分层性，可以计算冰川载荷变化引起的地球表面变形及内部应力状态的变化.利用它研究了挪威北海北部1.1 Ma以来的冰川载荷变化、特别是两万多年以来冰盖的消退引起的地表冰后回弹.结果表明，自2万年以来，冰后回弹效应在冰盖载荷变化的不同阶段呈现明显的时空变化，现今地表垂直变化速率为几个毫米/年，与观测结果一致.下地壳和上地幔的黏弹性松弛效应明显，上地壳的应力状态在现今海岸线两侧存在差异性，水平和垂直正应力变化可达几十兆帕，剪应力变化有一个先增加后迅速减小至零的过程，与古地震、现今地震时空分布及应力测量结果也比较符合，研究结果有助于加深对冰后回弹的动力学过程的认识.
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| 关 键 词： | 黏弹性 有限元 冰后回弹 流变性 冰川 |
| 收稿时间： | 2019-11-01 |
The study of post-glacial rebound and stress evolution since the Last Ice Age in the northern North Sea of Norway by using viscoelastic finite element model |
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| MENG Qiu,HU CaiBo,SHI YaoLin.The study of post-glacial rebound and stress evolution since the Last Ice Age in the northern North Sea of Norway by using viscoelastic finite element model[J].Chinese Journal of Geophysics,1954,63(10):3751-3763. |
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| Authors: | MENG Qiu HU CaiBo SHI YaoLin |
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| Institution: | Key Laboratory of Computational Geodynamics of Chinese Academy of Sciences, College of Earth and Planetary Sciences, University of Chinese Academy of Sciences, Beijing 100049, China |
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| Abstract: | A large area of ice sheet existed in the northern North Sea of Norway during the Last Ice Age. The loading and unloading of the ice sheet will have an important effect on the surface deformation and internal stress adjustment. We independently developed a Maxwell viscoelastic finite element program, according to the initial stress method. We considered many factors, such as gravity and tectonic loading, longitudinal and transverse inhomogeneity of the elasticity of the earth medium and stratification of viscosity. We can calculate the deformation of the Earth's surface and the change of the internal stress state caused by glacial load changes. A numerical simulation is carried out for the surface postglacial rebound caused by the change of glacial load since 1.1 Ma, especially after the retreat of ice sheets since about 20,000 years ago, in the northern North Sea of Norway. The results show that the postglacial rebound effect shows significant spatiotemporal variation in different ice sheet stages since 20,000 years, and the current surface vertical rate is several millimeters per year, which is consistent with the observed results. The effect of lower crust and upper mantle viscoelastic relaxation is obvious. The crustal stress state is very different near the current coastline, both for the horizontal and vertical normal stress changes, which can reach tens of MPa. Shear stress increase from the start of unloading until 10,000 year BP, and then rapidly decrease to zero. The spatiotemporal changes of stresses caused by ice sheet evolution are consistent with the diversity of paleo and modern seismicity and stress measurement data. The numerical work will deepen the understanding of the dynamical process of ice after the rebound. |
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| Keywords: | Viscoelasticity Finite element model Postglacial rebound Rheology Glacier |
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