新疆于田地区2008年以来3个地震 序列的参数早期特征

考察新疆于田地区2008年以来发生的2008年3月21日M_S7.3、 2012年8月12日M_S6.3和2014年2月12日M_S7.3等3个地震序列的参数早期特征， 利用“时空传染型余震序列”(ETAS)模型进行了参数估计. 统一选用截止震级M_c=M_L3.0， 并使用最大似然法分别估算了这3个序列不同持续时间的α、 p和b等参数. 研究结果表明， 3个地震序列的参数差异明显， 其中: 2014年M_S7.3地震序列α值与2012年M_S6.3地震序列接近， 但高于2008年M_S7.3地震序列； 2014年M_S7.3地震序列p值较低， 表明当前序列衰减缓慢； 2012年M_S6.3地震序列b值最大， 2014年M_S7.3地震序列次之， 2008年M_S7.3地震序列最小. 此外， 2008年M_S7.3地震序列参数在震后20天内变化较为显著， 而2014年M_S7.3地震序列的α值和p值在震后3.5天内则相对稳定. 

Parameter characteristics in the early period of three earthquake sequences in the Yutian,Xinjiang since 2008

To investigate the characteristics of various earthquake sequences, we fitted three aftershock sequences of the March 21, 2008 M_S7.3 earthquake, the August 12, 2012 M_S6.3 earthquake, and the February 12, 2014 M_S7.3 earthquake respectively with the epidemic-type aftershock sequence (ETAS) model. We set a unified cutoff magnitude M_c=M_L3.0 and adopted the maximum likelihood method to estimate the parameters α, p and b of these sequences with different duration times. It is observed that the α, p and b value are significantly different for the three earthquake sequences. The α value of 2014 M_S7.3 earthquake sequence is close to the 2012 M_S6.3 earthquake sequence, and larger than that of the 2008 M_S7.3 earthquake sequence; a smaller p value of the 2014 M_S7.3 earthquake sequence indicates that it has a slow decay rate of aftershocks compared with the other two sequences; the b value of 2014 M_S7.3 earthquake sequence is larger than the 2008 M_S7.3 earthquake sequence, but smaller than the 2012 M_S6.3 earthquake sequence. Moreover, the parameters of 2008 M_S7.3 earthquake sequence change significantly within 20 days after the mainshock, while the α and p values of the 2014 M_S7.3 earthquake sequence keep stable in the first 3.5 days.