【摘要】 在利用双差定位法对2003年7月21日、10月16日云南大姚先后发生的6.2级、6.1级地震序列进行精定位的基础上,采用互相关系数法测量了两个地震序列的快波偏振方向和快慢波的延迟时间.结果表明:①两个地震序列的S波分裂现象较明显,除三台乡台以外,大部分台站记录到的地震快波平均偏振方向与区域最大水平主压应力方向基本一致,三台乡台的偏振方向出现两个峰值,平均偏振方向是N80°E,表现出与区域最大水平主压应力方向不一致的现象;②序列延迟时间与震源深度之间没有明显规律性关系,但不同延迟时间范围内偏振方向表现出不同的规律;③两次地震序列S波分裂结果对比发现,6.2级地震序列快波的偏振方向明显较分散,快波平均偏振方向比6.1级地震序列大20°,而延迟时间方面二者相差不大;④S波分裂快波偏振方向所表现出的空间差异性,可能是由于在区域背景应力场的基础上叠加了两次6级主震产生的应力扰动引起的.更多还原

【Abstract】 The polarization direction of fast wave and the delay time between fast and slow wave were measured for two earthquake sequences occurred continuously on 21 July (M=6.2) and 16 October (M=6.1) in Dayao, Yunnan in 2003 using cross-correlation coefficient method, after determining the high-resolution hypocentral locations of the earthquake sequences using the double-difference earthquake location algorithm. The results indicated that. ① The phenomena of S wave splitting are obvious in the two earthquake sequences, and the average polarization directions of fast wave in most stations are almost consistent with regional maximum horizontal compressive stress direction except the station Santai. There are bimodal fast directions in the polarization directions at station Santai and the mean polarization direction is N80°E, indicating an inconsistent phenomenon referred to regional maximum horizontal compressive stress direction. ② There is no apparent relation between delay time and focal depth in the sequences, but the polarization direction show different character in different delay time range. ③ The comparison of S wave splitting results in the two earthquake sequences show that the polarization direction in M=6.2 earthquake sequence is more scattered and its average fast direction is 20° larger than that of M=6.1 sequence, and the delay times between two sequences show a little difference. ④ The spatial variation in S wave splitting polarization direction may be due to the stress disturbance imposed by the two M=6 mainshocks on regional background stress field.更多还原