| 1976年MS7.8唐山地震断层动态破裂及近断层强地面运动特征 |
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| 引用本文： | 杜晨晓,谢富仁,张扬,史保平.1976年MS7.8唐山地震断层动态破裂及近断层强地面运动特征[J].地球物理学报,2010,53(2):290-304. |
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| 作者姓名： | 杜晨晓 谢富仁 张扬 史保平 |
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| 作者单位： | 1.中国地震局地壳应力研究所，北京 100085;2.中国科学院研究生院，北京 100049 |
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| 摘 要： | 采用美国南加州地震委员会（SCEC）Steven Day博士提供的三维有限差分断层瞬态破裂动力学模型（3D-FDM），以1976年唐山MS7.8地震为例，从简化的断层双侧破裂模式出发，对该地震发震断层的动态破裂过程及近断层地表运动特征进行了仿真模拟和计算.研究区域为围绕发震断层200 km×140 km×40 km（深度）的长方形块体组成，模拟计算的空间分辨率和时间分辨率分别为200 m和0.012 s，形成的空间网格节点数为1051×701×201.在DELL小型工作站上，我们实现了对源程序的移植和并行计算.同时，通过引进计算机可视化技术，对模拟数据进行了3D/4D解释分析.另外，在对源程序修改过程中，实现了对京津唐地区三维地壳速度结构的嵌入，在一定程度上增强了对地震波传播以及地面运动模拟的真实性，并讨论了地震破裂的方向性对近断层地表运动的影响.最后根据初步研究结果结合京津唐地区活动断层构造特征，对唐山MS7.8级主震后随之而来的1976滦县MS7.1级余震及宁河MS6.9级余震的动态触发机制提出了新的解释.由于受主震破裂方向性作用的影响，使得主震对后续两个较大余震产生的动态应力变化的峰值在断层的走滑方向上较大，为2~3 MPa，在逆冲方向上较小,为0.1~0.2 MPa.即唐山主震的发生使得其周边的应力场有一个瞬态的应力调整，唐山主震对后续余震的发生有促发作用.
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| 关 键 词： | 有限差分模型 动态破裂 强地面运动 破裂传播方向性 余震触发机制 |
| 收稿时间： | 2009-02-19 |
| 修稿时间： | 2009-09-21 |
3D modeling of dynamic fault rupture and strong ground motion of the 1976 MS 7.8 Tangshan earthquake |
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| DU Chen-Xiao,XIE Fu-Ren,ZHANG Yang,SHI Bao-Ping.3D modeling of dynamic fault rupture and strong ground motion of the 1976 MS 7.8 Tangshan earthquake[J].Chinese Journal of Geophysics,2010,53(2):290-304. |
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| Authors: | DU Chen-Xiao XIE Fu-Ren ZHANG Yang SHI Bao-Ping |
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| Institution: | 1.Institute of Crustal Dynamics, China Earthquake Administration, Beijing 100085, China;2.Graduate University of Chinese Academy of Sciences, Beijing 100049, China |
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| Abstract: | Using 3D finite difference code developed by Dr. Day in SCEC, we simulated fault dynamic rupture process and associated near-fault strong ground motion for the 1976 MS7.8 Tangshan earthquake based on a simplified bi-lateral rupture model and slip-weakening frictional law. The fault length, width, and depth of the model are 200 km, 140 km, and 40 km, respectively. The discretized space and time steps are 200m and 0.012 s, respectively, which make the total number of node points up to 0.15 billion. In the implementation level, a parallel computational algorithm has been developed in DELL work station, and a computer visualization technique has been used in the numerical simulation in order to do data analysis. Furthermore, a regional 3D velocity model also has been embedded into the model to simulate seismic wave propagation and associated ground motion. According to the numerical results, we discussed the characteristics of the ground motions produced from the 3D rupture model with associated 3D velocity structure, including PGA and PGV distributions around fault. A physics based explanation related to the rupture directivity is also proposed to show that the radiated SH-type particle motion (fault-normal component) from ruptured fault has a significant influence on the near fault ground motion along the fault strike direction. Based on the radiated SH wave motion and propagation caused by directivity effect, we proposed that, for the 1976 MS7.1 Luanxian and MS6.9 Ninghe earthquakes, a dynamic triggering mechanism related to the temporal stress variation could play a significant role to trigger these two events. The result shows that the dynamic stress change could reach 2~3 MPa in strike direction and 0.1~0.2 MPa in thrust direction. |
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| Keywords: | Finite difference model Dynamic rupture Strong ground motion Rupture directivity Dynamic trigger |
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