| 龙门山断层地震周期及其动力学过程模拟研究 |
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| 引用本文： | 马林飞,陶玮,张永,曾明会,郑茜.龙门山断层地震周期及其动力学过程模拟研究[J].地球物理学报,2018,61(5):1824-1839. |
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| 作者姓名： | 马林飞 陶玮 张永 曾明会 郑茜 |
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| 作者单位： | 1. 中国地震局地质研究所地震动力学国家重点实验室, 北京 100029;2. 大连理工大学海岸与近海工程国家重点实验室, 辽宁大连 116024;3. 航天神舟智慧系统技术有限公司, 北京 100029 |
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| 基金项目： | 国家自然科学基金项目（41374103）资助. |
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| 摘 要： | 在断层面上引入速率-状态相依摩擦本构关系、考虑铲形逆冲断层几何结构特征、断层下盘和上盘中下地壳及上地幔为黏弹性介质、上盘上地壳为弹塑性介质，本文用二维有限元动力学模型模拟了龙门山断层上大震准周期复发行为、分析了断层上地震孕育位置、地震周期不同阶段的应力/应变场演化特征.不同于近垂直走滑断层上的地震周期行为，大陆铲形逆冲断层上的构造应力的积累和释放过程更复杂、有其独特性.我们得到如下认识：（1）铲形逆冲断层上的地震复发是准周期行为.（2）龙门山断层最大库仑应力位于断层17~20 km深处，应力长期积累和同震释放都在此深度最大，说明地震会在此处孕育、发动.（3）在断层破裂的深部和浅部，同震滑动大小和构造应力释放大小并非同步，而是差异悬殊.（4）地震仅部分释放区域积累的应变能，断层上盘上地壳顶部和底部的褶皱、破裂等永久变形形式也是释放应变能的重要形式.（5）应变能密度增量的演化图像分为：震间、同震、震后期，清晰反应了龙门山断层附近的地震动力学过程.（6）地震发生除释放能量外，同时也对近断层的中地壳和断层底部有很大的应变能加载；这些加载，在震后期可能通过震后滑移、余震或中下地壳乃至上地幔的驰豫形变用几十年时间释放.以上对大陆内铲形逆冲断层上变形特征的了解，有助于我们在其地震周期行为中评估地震危险性.
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| 关 键 词： | 铲形逆冲断层 龙门山断层 地震周期行为 速率-状态相依摩擦本构关系 动力学模型 |
| 收稿时间： | 2018-03-06 |
The numerical simulation study of the earthquake cycles and the dynamic evolutionary processes on the Longmen Shan Fault |
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| MA LinFei,TAO Wei,ZHANG Yong,ZENG MingHui,ZHENG Qian.The numerical simulation study of the earthquake cycles and the dynamic evolutionary processes on the Longmen Shan Fault[J].Chinese Journal of Geophysics,2018,61(5):1824-1839. |
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| Authors: | MA LinFei TAO Wei ZHANG Yong ZENG MingHui ZHENG Qian |
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| Institution: | 1. State Key Laboratory of Earthquake Dynamics, Institute of Geology, China Earthquake Administration, Beijing 100029, China;2. State Key Laboratory of Coastal and Offshore Engineering, Dalian University of Technology, Dalian Liaoning 116024, China;3. Aerospace ShenZhou Smart System Technology Co., Ltd., Beijing 100029, China |
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| Abstract: | We simulate the earthquake dynamic process of Longmen Shan fault over earthquake cycles using a 2-D finite element model, taking into account of the fault geometry, media mechanical property, and rate-state friction law on fault. The system is driven laterally by constant tectonic loading and gravity. The tectonic stress accumulation and release on a continental listric fault system have some unique features comparing with those of a vertical strike-slip fault system. Based on numerical simulation of stress/strain evolution over earthquake cycles, we find that: (1) Quasi periodicity of earthquake cycles emerged in the simulation. (2) The maximum Coulomb stress and Mises stress accumulating and releasing are located in the depth of 17~20 km, where probably is the seismogenetic region on the fault. (3) The coseismic slip and Coulomb stress release show a disparity between the upper and lower part of the fault rupture, with larger slip and lower stress release near surface and smaller slip and greater stress release at down dip of the fault rupture consistent with seismic and geodetic coseismic study results. (4) Tectonic stress and strains are accumulated interseismically, and released partially by periodical and partially by the permanent deformation and folding in upper crust. (5) The dynamic process of earthquake cycle is demonstrated clearly by the strain energy density increment patterns during the interseismic, coseismic and poseismic periods. (6) Strain energy also accumulated within the lower part of the seismogenic layer during the coseismic time period, and can be released post-seismically through aftershock and viscous deformation close to fault around the downdip end of the fault rupture. The result will enhance our knowledge on fault zone physical process deformation mechanisms. Characterization of these deformation features helps assess seismic potentials over an earthquake cycle. |
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| Keywords: | Listric thrust fault Longmen Shan fault Earthquake cycle Rate-state friction law Dynamic modeling |
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