0引言2008年5月12日M_W7.9汶川地震近5年之后,在距汶川地表破裂南端西南约45km处,发生了4月20日M_W6.6芦山地震(Han et al,2014;Zhang et al,2014;图1)。这两个事件如此近的空间和时间距离表明后面的事件是前面事件的余震,换句话说,前面的事件对后面事件发生所起的作用比长期构造加载作用大。前人对这个问题的研究有不同的看法。一方面,Du等(2013)、Liu等(2013)和Xu等(2013)认为这两个事件为互不相关的独立事件。另一方 0 Introduction May 12, 2008 After nearly 5 years of M_W7.9 Wenchuan earthquake, the M_W6.6 Lushan earthquake on April 20 occurred about 45 km southwest of the southern end of the Wenchuan surface rupture (Han et al, 2014; Zhang et al , 2014; Figure 1). The close spatial and temporal distances between the two events indicate that the latter event is the aftershock of the preceding event. In other words, the preceding event plays a greater role than the long-term construct in loading the latter event. The predecessors have different opinions on this issue. On the one hand, Du et al. (2013), Liu et al. (2013) and Xu et al. (2013) consider these two events as independent events that are not related to each other. The other party