云南盈江地区中强地震序列特征分析

Features of the medium-strong earthquake sequences in Yingjiang,Yunnan Province

基于云南数字地震台网记录的2008年、2011年和2014年盈江地震序列资料,采用双差定位方法对盈江地区3组6次中强地震序列进行重定位,分析其空间分布特征,结果显示序列分布的优势方向主要为北东向和近南北向。采用Brune模型理论,计算盈江地震各序列震源参数。分析了各地震序列应力降与震级的关系,研究表明应力降随震级增大有着某种增大的趋势,4.0级以下地震应力降与震级关系不显著,4.0级以上地震的应力降与震级有一定的线性趋势相关性,随震级增大而增大是显著的。分析了各地震序列应力降的统计特征,结果表明2008年8月、2011年3月和2014年5月地震的前震序列累积应力降值约为20 MPa左右,大致相当的前震序列应力降值是盈江3个地震序列的主要特征。

Selecting the data of three earthquake sequences in Yingjiang,Yunnan Province in 2008,2011 and 2014 recorded by the Yunnan Digital Seismic Network,we use the double-difference location method to relocate 6 medium-strong earthquakes in these sequences.We find that the sequences distribute mainly in northeast and north-south directions.Then,according to the Brune Dislocation Model,we calculate the source parameters of these three sequences.Further,we analyze the correlation between the magnitude and the stress drop of the sequences;the stress drop has no significant correlation with the magnitudes under 4.0,however it has a linear correlation with the magnitudes over 4.0.Moreover,the higher the magnitude rises,the more obvious the correlation is.We also find that the stress-drop values of the foreshock sequences of the three earthquake sequences are all roughly equivalent to 20 MPa.