云南及周边地区Lg尾波Q值的分布特征

DISTRIBUTION CHARACTERISTICS OF Q VALUE OF THE Lg CODA IN YUNNAN AND ITS ADJACENT REGIONS

收集了昆明台 1990～ 2 0 0 0年间大于 4 .0级的地震宽频记录资料 ,以及分布在云南境内的 2 3个昆明数字化台网 1999～ 2 0 0 0年的资料 ,使用单台叠加谱比方法处理了 2 80个Lg尾波信号 .在假定Lg尾波Q与频率f有Q=Q0 fη关系的基础上 ,计算出各射线 1Hz时的Q值及频率相关因子 η .在此基础上 ,运用反投影技术反演得到云南及周边地区 0 .5°× 0 .5°网格内的Q0 和 η的分布图像 .结果表明 :云南及周边地区的Q0 在 15 0～ 30 0之间变化 ,滇东地区的Q0 明显高于滇西地区 ;η的变化范围在 0 .3～ 0 .8之间 ,绝大部分地区 η的变化范围为 0 .5～ 0 .6 .

We have collected broadband seismograms of earthquakes with magnitudes greater than 4.0 recorded by the Kunming station during the period 1990～2000 and 23 Kunming digital network stations located in Yunnan province during the period 1999～2000. The total 280 Lg coda traces are studied using the stack spectral ratio (SSR) method. Supposing Q of Lg coda correlates with frequency, f by Q=Q 0f η, the Q value at 1Hz, Q 0 and η for each record are calculated. Based on the calculated results, the distribution maps of Q 0 and η for 0.5°×0.5° cells are obtained using the back-projection technique. The results indicate Q 0 in Yunnan and its adjacent regions exhibits low values, varying between 150 and 300. Q 0 in eastern Yunnan is higher than that in western Yunnan. η varies between 0.3 and 0.8. For most of the study regions η is within the range between 0.5 and 0.6.