【作者】 王力伟；

【导师】 陈棋福；

【作者基本信息】 中国地震局地震预测研究所 ， 固体地球物理， 2010， 硕士

【摘要】 人们常用地震产生的静态库仑应力变化解释地震的空间迁移和余震的空间分布规律,但是,在静态库仑应力计算时,却面临着室内试验数据和观测资料无法对计算所涉及的参数进行足够约束的困难。参数取值的不确定性会直接影响到静态库仑应力的计算结果。因此,有必要对静态库仑应力计算的参数敏感性和实际应用做更全面的研究。在分析地震触发的静态库仑应力计算的不确定性研究中,本论文以研究资料十分丰富的汶川地震为例,首先根据川滇地区的断裂活动数据构建了研究区的接收断层矩阵,并以此作为投影断层面,计算了研究区的2D静态库仑应力变化图像,作为分析比较的基本模型,然后依次改变基本模型中的计算参数,计算结果直观的揭示了不同计算模型和参数选取对汶川地震产生的静态库仑应力场计算的影响。分析得出:重力、接收断层位置和走向的影响较小,而其他参数的不同选取均会对静态库仑应力变化量值和符号造成不同程度的影响,对地震破裂面周边的影响尤其明显,计算时的参数敏感性分析不可忽略。在分析主震产生的静态库仑应力变化对余震分布的影响时,采用两种方式计算了汶川地震对余震的触发效应,1.计算主震在余震的最优走滑破裂面上的静态库仑应力变化,2.采用不同地震位错模型和等效摩擦系数,计算主震在余震节平面上产生的静态库仑应力变化。通过统计处于静态库仑应力增加区域的余震占余震总数的比例,得到:余震有一半以上被主震产生的静态库仑应力触发,触发率最大84%,余震的触发率随着等效摩擦系数的增加而增大,符合汶川逆冲型地震断层破裂面具有较大等效摩擦系数的破裂机制。在静态库仑应力快速产出应用研究中,及时计算了2010年4月玉树7.1级地震产生的最优库仑应力变化和静态库仑应力在震源区活动断裂上的分布。结果表明:玉树地震使断层破裂面西北端和东南端出现应力增加,使甘孜-玉树断裂西北段和东南段、清水河断裂中段、杂孕-楚玛尔河断裂中段、杂多-上拉秀断裂西北段、扎那曲-着晓断裂中段、字嘎寺-德钦断裂西北和东南段应力增加。计算结果能为此区域地震危险性分析提供一定参考。更多还原

【Abstract】 Static Coulomb stress change induced by earthquake slip is used frequently to explain earthquake activities and aftershocks distribution. However, some parameters for the Coulomb stress calculation are unable to be well constrained from laboratory experiments and field observations. Different parameters may directly affect the calculation results of static Coulomb stress. Therefore, it is necessary to do a more comprehensive study on the uncertainty and application of static Coulomb stress change triggering.To investigate uncertainty of static Coulomb stress change induced by earthquake, this study takes the well-studied Wenchuan earthquake as an example. We first build the receiver fault matrices of the study area, with smooth interpolation of fault geometry and rake between the Sichuan and Yunnan`s major active faults data, and take the matrices as a projection plane. Then we calculate the 2D image of static Coulomb stress change of the study areas as a basic model to compare and analysis. To investigate how the parameters affect the calculation results, we change the parameters in turn through modeling and directly compare the results of different calculation parameters. We find that gravity, receiver faults position and strike have little influence on coseismic Coulomb stress change calculation, but other parameters can change the value and sign of the results in various degrees especially around the earthquake rupture plane. Therefore the uncertainty of the static Coulomb stress change induced by earthquake should be taken into consideration in the earthquake hazard analysis.To analyze the influence of the static Coulomb stress change induced by the main shocks on the aftershock distribution, we adopt two ways for quantifying the static Coulomb stress change induced by Wenchuan earthquake associated to its aftershock distribution. We first calculate the static Coulomb stress change on the optimally oriented receiver fault plane; then further calculate the static Coulomb stress change on each aftershock nodal planes with different slip model and apparent fault friction. Through counting the proportion of aftershocks in the stress increased areas to the whole, we find that more than half of the aftershocks were triggered by static Coulomb stress change induced by the main shock with maximum triggered rate 84%. The triggered rate is proportional to the apparent fault friction, which is consistent with the Wenchuan earthquake`s thrust mechanism that usually accompanies with a large apparent friction value.Using the Coulomb stress change as a fast output tool, we compute the Coulomb stress change induced by the 14 April 2010 Ms7.1 Yushu earthquake on optimally oriented faults and its neighborhood faults. Our result shows that the Coulomb stress has increased on the northwest and southeast end of the rapture fault. The earthquake also increased on the northwest and southeast of Ganzi-Yushu, Ziga temple-Deqin, the central segment of Qingshuihe, Zayun-Chumaer, Zhalaqu-Zhexiao and the northwest of Zaduo-Shanglaxiu fault. The calculation results can help to refine the seismic hazard analysis of the region.更多还原