孙云强,
罗纲^,
中国科学院计算地球动力学重点实验室, 地球与行星科学学院, 中国科学院大学, 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: 孙云强, 博士研究生, 主要从事地球动力学数值模拟方面的研究.E-mail:sunyunqiang15@mails.ucas.ac.cn

通讯作者: 罗纲, 教授, 主要从事理论和应用计算地球动力学方面的研究.E-mail:gangluo@ucas.ac.cn

中图分类号: P315;P541

收稿日期:2017-07-03
修回日期:2017-09-07
上线日期:2018-06-05

Spatial-temporal migration of earthquakes in the northeastern Tibetan Plateau: Insights from a finite element model

SUN YunQiang,
LUO Gang^,
Key Laboratory of Computational Geodynamics, College of Earth and Planetary 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: 03 July 2017
Revised Date: 07 September 2017
Available Online: 05 June 2018


摘要
摘要:地震在大陆内部断层系统中的时空迁移和丛集的基本力学机制一直是地球科学家关注的重要问题.青藏高原东北缘地震活动频繁，其地震时空迁移和地震丛集现象显著，是研究这个问题的重要区域.我们建立了一个三维黏弹塑性有限元模型，模拟了青藏高原东北缘主要活动断层系统的地震循环和地震时空迁移；计算了断层系统的应力演化；并探讨了断层之间的相互作用及地震时空迁移和地震丛集的原因.模拟结果显示断层之间的相互作用通过增加或降低断层上的库仑应力，加速或延缓了地震发生，使得区域地震可以在短时间内集中发生，从而形成地震丛集；另外，区域经过多个地震循环的长期演化，一些孕震断层上的应力状态恰好都达到屈服的临界状态附近，从而也可以导致这些断层上的地震在短期内集中发生，因此产生地震丛集和地震迁移.我们发现当区域经历地震丛集之后，该区域的应力大大释放，区域进入地震平静期；随着构造加载的持续，区域应力逐渐恢复，为下一次地震丛集或地震序列累积应力和能量；上述过程可以重复发生.因此地震丛集期与平静期交替出现.我们还统计了各个断层的大地震相互迁移的模拟结果，结果显示青藏高原东北缘下一次大地震有很大的概率会发生在海原断层上.
关键词: 青藏高原东北缘/
地震时空迁移/
地震丛集/
黏弹塑性有限元模拟/
库仑应力变化

Abstract:The spatial-temporal migration of earthquakes and the mechanism of earthquake clustering in continental interiors are an issue receiving much attention. The northeastern margin of the Tibetan Plateau is a seismically active region, where major earthquakes migrate and cluster in both time and space remarkably. We construct a three-dimensional viscoelastoplastic finite element model to simulate earthquake cycles and spatial-temporal migration of earthquakes along major fault systems in this area. We calculate stress evolution of these fault systems, investigate fault interactions, and explore the mechanisms of spatial-temporal migration of earthquakes and earthquake clustering. Modeling results show that fault interactions accelerate or retard the future earthquakes on faults by increasing or decreasing Coulomb stress on these faults, and thus earthquakes can occur sequentially in a short time leading to an earthquake cluster. In addition, after long-term stress evolution over multiple earthquake cycles, stresses on some seismogenic faults may be close to the critical state of failure which can also result in sequential occurrence of earthquakes in a short time, an earthquake cluster as well as earthquake migration. We find that stresses in the region are largely released after an earthquake cluster, and then it enters a period of seismic quiescence. Afterwards with continuous tectonic loading, regional stresses gradually recover towards next earthquake cluster or earthquake sequence. This processes can be repeated, and hence the period of earthquake clusters and the period of seismic quiescence occur alternately. We also analyze modeling results of migration of great earthquakes (M_W ≥ 7) on the major faults in this region, and our analysis predicts that in the northeastern margin of the Tibetan Plateau, the next big event following the 1920 M8.5 Haiyuan earthquake and 1927 M8 Gulang earthquake would occur most likely on the Haiyuan fault again.
Key words:Northeastern margin of the Tibetan Plateau/
Spatial-temporal migration of earthquakes/
Earthquake cluster/
Viscoelastoplastic finite-element model/
Coulomb stress change



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