祁连山冰川消融对地表变形、地应力和断层地震危险性时空变化的影响

doi:10.7523/j.issn.2095-6134.2021.05.006

摘要/Abstract

摘要： 随着全球气候不断变化，祁连山地区广泛存在的现代冰川，可能会进一步消融乃至完全消失，从而引起祁连山地区的地表变形、地应力及断层地震危险性的时空变化。利用自主开发的平面应变黏弹性有限元程序，计算在冰川不断消融引起的地表载荷和两侧地块的构造挤压作用下，1956-2106年共150 a期间，祁连山地区自地表变形、地应力的时空演化。重点关注祁连山地区典型地质剖面的主要断层的正应力、剪应力及库仑应力随时空的变化，定量评估各个断层地震危险性的变化。结果表明，在祁连山冰川不断消融的情况下，祁连山地区地表抬升速率呈现先快速增加后趋于稳定的冰后回弹现象；研究区域的水平应力、垂直应力及剪应力在冰川载荷卸载和边界构造加载的双重作用发生显著变化；大柴旦-宗务隆山断裂、哈拉湖南山断裂和哈拉湖盆地北缘断裂库仑应力变化持续增大，未来地震危险性增强；阴凹槽断裂和祁连山北缘断裂库仑应力增加很小，反映了在冰川融化影响不大、仅仅在构造应力增加为主的情况下，地震危险性随时间增加是缓慢的。

关键词: 有限元, 黏弹性, 地震危险性, 祁连山, 冰川

Abstract: With the continuous development of global climate change, the widespread modern glaciers may further melt or even completely disappear, resulting in the temporal and spatial changes of surface deformation, stress, and fault seismic risk in Qilian Mountains. In this paper, a plane-strain viscoelastic finite element program was developed to calculate the spatial and temporal evolution of surface deformation and ground stress in Qilian Mountains during the 150-year period from 1956 to 2106 under the surface load caused by glacier melting and the continuous tectonic compression. We calculated the normal stress, shear stress, and the change of Coulomb stress on the main faults in Qilian Mountains. The changes of seismic risk on each fault were quantitatively estimated. The surface uplift rate of Qilian Mountains is controlled by the ice rebound. The surface uplift rapidly increase at the beginning and then tends to be stable under the continuous melting of Qilian Mountains glacier. The horizontal stress, vertical stress, and shear stress change obviously under the effects of glacier melting and boundary tectonic loading. The Coulomb stress changes ΔCFS of the DZF, HSF, and HNF continuously increase, and the seismic risk increases in the future. Coulomb stress changes on the YAF and QNF faults are very small, and the seismicity seismic risk changes little. The numerical simulation provides a theoretical reference for understanding the spatial and temporal variation of future earthquake risk in Qilian Mountains under the glacier melting and tectonic loading.

Key words: finite element model, visco-elasticity, seismic risk, Qilian Mountains, glacier

中图分类号:

P315

孟秋, 胡才博, 石耀霖. 祁连山冰川消融对地表变形、地应力和断层地震危险性时空变化的影响[J]. 中国科学院大学学报, 2021, 38(5): 624-631.

MENG Qiu, HU Caibo, SHI Yaolin. Effects of glacier ablation on surface deformation, stress field, and seismic risk of main faults in Qilian Mountain area[J]. Journal of University of Chinese Academy of Sciences, 2021, 38(5): 624-631.

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