摘要
本文采用CAP方法反演了2011年两次岷县中等地震的震源机制解,首先讨论了方位角对反演结果的影响,通过对不同方位角组合的比较,得到的结果比较稳定,进一步得出两次地震的震源机制解.然后,采用自助抽样(bootstrap)方法,基于CAP方法进行多次重复反演,得到岷县两次中等地震事件的大样本量震源机制解数据.基于这些大样本数据,以Kagan角为目标函数,利用粒子群非线性优化方法搜索震源机制解的优化解,并估计了震源机制解的误差范围,M_S4.0、M_S4.5的误差分别为6.0°和18.3°.结果分析表明,CAP结果与得到的优化解基本接近,其误差在可接受的误差范围内.
We accept the Cut and Past（ CAP） method to inverse the focal mechanisms of the two Minxian moderate earthquakes and discuss error estimation for the inversion in this paper. First,we inverse the focal mechanism with combinations of different azimuth stations used the CAP method and the results show that the azimuth has little effect on the inversion. And we select a dozen stations to calculate the focal mechanisms of the two Minxian moderate earthquakes. Then,We sample by equal probability randomly the waveforms of the two earthquakes recorded by the seismic station and employ these data repeating inversion procedure. We obtain1000 focal mechanisms by 1000 times inversions. Based on these solutions,we employ the PSO（ Particle Swarm Optimization）algorithm to confirm the optimal solution when the Kagan angle is minimal to all the double couple models and evaluate the uncertainty range of the inversion result using its standard deviation. The error of solutions are separately ± 6. 0° and ± 18. 3° for the Minxian earthquakes with MS4. 0 and MS4. 5. Meanwhile,We project P and T axes of bootstrap results onto a focal sphere and achieve the probability density distribution of focal mechanisms. We conclude that the method demonstrated in this paper is not confined to achieve more accurate focal mechanisms and obtain inversion error,while it can be used to exclude isolate and incorrect solutions effectively and avoid the effect of data from station azimuth. Therefore,the CAP method can be applied to get reliable solution automatically immediately after a moderate earthquake occur.
作者
王丽霞
张辉
李赫
WANG Li-xia;ZHANG Hui;LI He(Lanzhou Institute of Seismology, CEA , Laazhou 730000, China;Earthquake Administration of Tianjin, Tianjin 300201, China)
出处
《地球物理学进展》
CSCD
北大核心
2017年第5期1930-1935,共6页
Progress in Geophysics
基金
中国地震局地震科技星火计划攻关项目(XH15042
XH14049)
国家自然科学基金项目(41304048)共同资助
