| 基于唐山7.8级地震探讨动态应力作用 |
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| 引用本文： | 陆明勇,郑文衡,陈连旺,牛安福,詹自敏,李民,寇建新,房综绯.基于唐山7.8级地震探讨动态应力作用[J].地球物理学报,2010,53(9):2110-2118. |
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| 作者姓名： | 陆明勇 郑文衡 陈连旺 牛安福 詹自敏 李民 寇建新 房综绯 |
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| 作者单位： | 1. 中国地震应急搜救中心,北京 100049;
2. 华中科技大学,武汉 430074;
3. 中国地震局地壳应力研究所,北京 100085;
4. 中国地震台网中心,北京 100045 |
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| 基金项目： | 地震科学联合基金项目，国家"十一五"科技支撑计划项目 |
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| 摘 要： | 运用三维非线性动态有限元方法(Non-linear Dynamic FEM)仿真模拟研究了菱形模型的动态应力作用,分析了1976年唐山7.8级地震.结果表明:(1)唐山地震前增强的中强地震产生的冲击力形成的应力波反射后发生半波损失, 成为动态的拉伸应力,通过减小内摩擦而引起岩石产生裂纹、局部破裂并发生串通,一方面触发地震,另一方面为孕育唐山地震积累能量,表现为正反馈过程.(2)唐山地震产生的冲击力加卸载存在时间差,造成加卸载冲击波相位不同,结果产生的动应力和围压叠加致使围压波动和下降,导致抗剪切强度降低,使初始破裂分别向北东、西南方向传播.(3)冲击力的卸载,相对于产生拉伸性的应力波,反射后发生半波损失,成为动态的压缩应力,致使围压增大并导致破裂停止;而动态应力在传播过程中衰减.因此,余震的发生是一个负反馈过程.
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| 关 键 词： | 唐山地震 三维非线性动态有限元方法 动态应力作用 低值波动 |
| 收稿时间： | 2009-12-24 |
Discussion of dynamical stress effect on Tangshan Ms7.8 earthquake |
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| LU Ming-Yong,ZHENG Wen-Heng,CHEN Lian-Wang,NIU An-Fu,ZHAN Zi-Min,LI Min,KOU Jian-Xin,FANG Zong-Fei.Discussion of dynamical stress effect on Tangshan Ms7.8 earthquake[J].Chinese Journal of Geophysics,2010,53(9):2110-2118. |
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| Authors: | LU Ming-Yong ZHENG Wen-Heng CHEN Lian-Wang NIU An-Fu ZHAN Zi-Min LI Min KOU Jian-Xin FANG Zong-Fei |
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| Institution: | 1. China Center for Earthquake Disaster Emergency and SAR, Beijing 100049,China;
2. Huazhong University of Science and Technology,Wuhan 430074,China;
3. Institute of Crustal Dynamics,CEA, Beijing 100085,China;
4. China Earthquake Network, Beijing 100045,China |
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| Abstract: | We use the three-dimensional non-linear dynamic finite element method to perform a modeling study on dynamical stress effects with a rhombic model and analyze the Tangshan M7.8 earthquake in 1976. The result shows that stress wave is generated by shock force which is produced by strengthened moderately strong earthquakes before the Tangshan earthquake, when this wave encounters a fault, the reflected stress wave, becomes tensile due to half-wavelength loss, which causes cracks, local rupture and crack linkage in the rock by reducing rock friction. On the one hand, other earthquakes are triggered. On the other hand, energy for the Tangshan earthquake is accumulated. This is a process of positive feedback. The shock force from the Tangshan earthquake during processes of loading and unloading has a time difference, this forms the different phase of shock waves. The dynamical stress produced by stress wave, superposed on the confining pressure, makes confining pressure reduce and change at low values. These effects can reduce shear strength and make the initial fracture of the Tangshan earthquake propagate toward northeast and southwest respectively. The unloading of shock force generated by the Tangshan earthquake is equal to producing the effect of tensile stress wave, the reflected tensile stress waves, having lost half-wavelength, become compressive ones which cause confining pressure increase and rupture stop. Meanwhile during the process of dynamical stress propagation, its amplitude decays. So the aftershock occurrence of the Tangshan earthquake is a negative feedback process. |
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| Keywords: | Tangshan earthquake The 3D non-linear dynamic finite element method Dynamical stress effect Pressure pulsation at low value |
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