利用FOCMEC方法计算震源机制解的影响因素分析——以九江—瑞昌Ms5.7地震为例

摘要

Based on polarities of P, SV and SH waves combining with their amplitude ratios, using the Focal Mechanism Determining Method of FOCMEC, taking JiuJiang-RuiChang MS5. 7 earthquake on Nov 26 2005 as an example, the influencing factors such as velocity structure model, focal positioning error, data of the first motion and amplitude ratios, distribution of stations and so on are analyzed. The result shows that fine velocity structure model in the study area is necessary in this method; the velocity error of each layer within 5% is negligible. Within the type 2 accuracy of the epicenter location error and the change of focal depth resulting in little change in incidence angle are of little impact on the focal mechanism solutions. Focal mechanism solutions can also be accurately obtained when the number of polarities and stations is relatively less. Therefore, FOCMEC is a stable and reliable method for determining the focal mechanisms of moderate-small earthquakes.%应用Snoke最新发展的利用P波、SV波和SH波的初动和振幅比联合计算震源机制解的方法(FOCMEC),以2005年11月26日九江—瑞昌MS5.7地震为例,分析速度结构模型、震源定位误差、初动与振幅比资料和台站分布等对计算震源机制解的影响.结果表明,FOCMEC方法应采用研究区内的精细速度结构模型,各层速度误差在5％内时,对计算结果影响较小；2类精度内的震中定位误差对计算结果影响较小；造成入射角变化不大的震源深度的误差对计算结果影响较小；在初动和台站数量较少时也能准确确定震源机制解.因此FOCMEC方法是一种稳定、可靠的计算中小地震震源机制解的方法.