| 断裂两盘岩性差异对汶川地震的影响 |
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| 引用本文： | 姚琪,邢会林,徐锡伟,张微.断裂两盘岩性差异对汶川地震的影响[J].地球物理学报,2012,55(11):3634-3647. |
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| 作者姓名： | 姚琪 邢会林 徐锡伟 张微 |
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| 作者单位： | 1. 活动构造与火山重点实验室,中国地震局地质研究所,北京 100029;2. 中国地震台网中心,北京 100045;3. Earth Systems Science Computational Centre(ESSCC),The University of Queensland,St.Lucia,QLD 4072.Australia;4. 国土资源厅航遥中心,北京 100083 |
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| 基金项目： | 国家自然科学基金，中国地震局地质研究所基本科研业务专项 |
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| 摘 要： | 岩性差异导致层间变形差异是常见的构造变形现象.龙门山断裂带中段北川—映秀断裂虹口至清平段,断裂上盘为坚硬的前震旦系褶皱基底,下盘则为软弱的前陆盆地沉积物,两者之间具有较大的岩性差异.本文利用基于R-minimum的有限元算法对在一个地震复发间隔内的断层活动进行非线性摩擦接触模拟.计算结果显示,上下盘泊松比的差异则对断层破裂时间及快体变形影响不大,但不同的泊松比条件下断层的破裂过程略有不同,而上下盘杨氏模量的差异能够延迟断层的破裂时间,延长破裂过程,扩大地震复发间隔,且扩大了下盘深度10 km以上和10 km以下地层变形的差异.双断坡构造能够通过深部的应力分解来削弱断层下盘深度10 km以上的变形,但是在上下盘岩性一致的情况下,双断坡构造推迟了主断层的滑动时间,延长了破裂过程,而在强硬上盘和软弱下盘共存的条件下,发育于软弱下盘的次级破裂并不能对主断层的破裂时间和破裂过程造成较大影响.北川—映秀断裂上盘强硬的彭灌杂岩和下盘软弱的含碳沉积地层对汶川地震双断坡式破裂的生成具有重要的促进作用.
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| 关 键 词： | 龙门山断裂带 汶川地震 杨氏模量 泊松比 摩擦接触 |
| 收稿时间： | 2011-02-19 |
Influence of lithologic differences on either walls of the fault on the Wenchuan earthquake |
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| YAO Qi
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XING Hui-Lin
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XU Xi-Wei
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ZHANG Wei.Influence of lithologic differences on either walls of the fault on the Wenchuan earthquake[J].Chinese Journal of Geophysics,2012,55(11):3634-3647. |
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| Authors: | YAO Qi XING Hui-Lin XU Xi-Wei ZHANG Wei |
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| Institution: | 1. Key Lab. of Active Tectonics and Volcano, Institute of Geology,China Earthquake Administration, Beijing 100029, China;2. China Earthquake Networks Center, Beijing 100045, China;3. Earth Systems Science Computational Centre(ESSCC),The University of Queensland,St.Lucia,QLD 4072.Australia;4. China Aero Geophysical Survey & Remote Sensing Center for Land and Resources, Beijing 100083, China |
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| Abstract: | It is a common phenomenon that lithologic differences cause different deformation between layers. This work focuses on the Longmenshan thrust zone, which is located at the eastern margin of the Tibet plateau. The 2008 Wenchuan earthquake occurred at the middle segment of the Longmenshan thrust zone, which is called Beichuan-Yingxiu fault. The section of Hongkou to Qingping of the Beichuan-Yingxiu fault is a thick skinned thrust fault in the interface of Precambrian Complex and stratified rock. There is large difference in material between the hanging wall and footwall. Based on the seismic reflection profile, focal mechanism solutions and coseismic surface ruptures of the Wenchuan earthquake, two two-dimensional models constrained by the low-resistivity and low-velocity layers were built across the Beichuan-Yingxiu fault to study the influence of dissimilar materials. We use the R-minimum strategy based the nonlinear finite element method to simulate contact behavior of the fault and deformation style in the upper crust in the time period of one earthquake recurrence interval. Totally 24 couples of different Young's modules of the hanging wall and footwall were tested. The results show the interaction of the tough complex in the hanging wall and carbon-containing stratified rock in the footwall. The difference in the Young's modules between the hanging wall and the footwall could increase the slip time of the fault, prolong slip progress and cause more vertical deformation at the depth less than 10 km in the footwall. On the other hand, the difference in the Poisson ratio has little effect on the fault behavior, but seems to have some influence on the slip progress. When the seismogenic structure is in the interface of dissimilar materials, the activity of fractures developed in the foreland basin in front of the thrust belt has limited effects both on the slip time and slip progress of the thrust fault, but they could decrease the deformation of layers shallower than 10 km in the footwall through slip partitioning. The tough Pengguan complex in the hanging wall and the soft stratified rock is one of the key factors of the two imbricate structures ruptured in the Wenchuan earthquake. |
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| Keywords: | Longmenshan thrust fault Wenchuan earthquake Young’s modulus Poisson ratio Frictional contact |
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