尹力,
罗纲^,
中国科学院计算地球动力学重点实验室, 中国科学院大学地球与行星科学学院, 北京 100049

基金项目: 国家自然科学基金（41574085，41590865）资助


详细信息

作者简介: 尹力, 男, 1989年生, 博士, 主要从事地球动力学数值模拟计算.E-mail:yinli19890601@126.com

通讯作者: 罗纲, 男, 1977年生, 教授, 主要从事理论和应用计算地球动力学.E-mail:gangluo@ucas.ac.cn

中图分类号: P315;P541

收稿日期:2017-05-23
修回日期:2017-09-15
上线日期:2018-04-05

Crustal deformation across the Longmen Shan fault zone from finite element simulation of seismic cycles

YIN Li,
LUO Gang^,
Key Laboratory of Computational Geodynamics of Chinese Academy of Sciences, University of Chinese Academy of Sciences, Beijing 100049, China



More Information

Corresponding author: LUO Gang,E-mail:gangluo@ucas.ac.cn

MSC: P315;P541

--> Received Date: 23 May 2017
Revised Date: 15 September 2017
Available Online: 05 April 2018


摘要
摘要:现今地壳变形数据显示横跨龙门山断裂带的地壳缩短速率低于3 mm·a^-1，如此小的地壳缩短速率与龙门山断裂带附近的长期地质造山（平均高程约4.5 km）形成强烈对比.我们构建并使用了一个二维平面应变黏弹塑性有限元模型来模拟龙门山断裂带的地震循环位移变化，从而探讨了短期变形与长期变形之间的关系.模型模拟了地震循环的各个阶段（震间加载期、同震瞬间和震后黏性松弛调整期）以及多个地震循环（万年尺度）的地表变形，揭示了变形在地震循环中是如何累积、释放、调整以及最终形成永久变形导致了造山.模拟结果显示，岩石圈流变结构以及断层几何形态均对地震循环的地表位移变化有着显著的影响.经过多个地震循环，青藏高原东缘整体产生水平缩短与增厚抬升，而四川盆地基本保持稳定，区域的水平缩短主要由断层位错及青藏东缘的缩短抬升来调解，造成了青藏东部与川西盆地的差异抬升.研究结果将地震循环时间尺度的短期变形与长期地质造山联系起来，帮助我们理解青藏高原东部的隆升机制.
关键词: 龙门山断裂带/
地震循环/
短期变形与长期造山/
黏弹塑性有限元模型

Abstract:The present-day crustal deformation data show the shortening rate is less than 3 mm·a^-1 across the Longmen Shan fault zone. Such a small shortening rate is a sharp contrast to the long-term orogeny with topographic relief of about 4.5 km. To address this issue, this work constructs a series of 2-D plane strain visco-elastic-plastic finite element models to explore the relationship between short-term and long-term deformation. We simulate the surface displacement of different stages (inter-seismic, co-seismic and post-seismic) in one seismic cycle, and the total displacement of multiple seismic cycles. The results show that permanent deformation leading to orogeny is generated after a seismic cycle. The rheological contrasts in the lithosphere and fault geometry have a significant effect on surface displacement distribution. After multiple seismic cycles, the eastern Tibetan plateau experiences overall uplift and shortening, while the Sichuan basin remains relatively stable. The shortening of the entire region is mainly accommodated by fault slip along the Longmen Shan fold-and-thrust zone, resulting in differential uplift between the eastern Tibetan plateau and the western Sichuan basin. Our model links the short-term deformation of multiple seismic cycles with long-term geologic orogeny, which helps the understanding of the uplift mechanism of the eastern Tibetan plateau.
Key words:Longmen Shan fault zone/
Seismic cycle/
Short-term and long-term deformation/
Visco-elastic-plastic finite element modeling



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