2013年广西平果震群尾波衰减特征研究

Research on characteristics of seismic wave attenuation for the earthquake swarm occurring in Pingguo County，Guangxi Zhuang Autonomous Region in 2013

摘要:

2013年6～7月在广西平果县中铝广西分公司3号排泥库附近出现密集小震群活动。本文搜集本次震群中146次可用于计算尾波的ML>1.0地震的近距离台站数字地震波形，利用波形高信噪比的尾波时间域信号，采用计算尾波品质因子QC(f)值的Sato模型，通过滤波及去除环境噪声，计算了地震波传播路径上的尾波QC(f)值；拟合QC(f)值与频率f之间的关系，分析了排泥库区域地震波衰减的时空特征。根据信噪比及计算要求，从近场7个台站的记录中挑选出273条三分向记录，计算尾波衰减参数，得到尾波QC(f)与频率f的关系为：Q(f)＝(69.07±40.09)f0.90±0.23。结果表明，本区域为低衰减区域，库区Q值相对较高，地震波衰减较慢，且Q值对频率的依赖性不强，研究区介质非均匀性程度低，介质较为稳定。

Abstract:

From June to July,2013，the small earthquake swarm occurred intensively nearby the third Mud Gallery of Aluminum Corporation of China Guangxi Branch which is located in Pingguo County，Guangxi Zhuang Autonomous Region. This paper have collected waveform data of 146 earthquakes with ML>1.0 recorded at the near-source stations. By using the coda time series with high signal-to-noise ratio and filtering the data to eliminate background noises based on Sato mode1，the coda QC(f) was calculated，and the relationship between QC(f) and frequency (f) was obtained. Then，the characteristics of seismic wave attenuation in the third Mud Gallery area were analyzed. 273 three-component records chosen from 7 seismic stations were used for this study. The result shows that the relationship between the QC(f) and f is：Q(f)＝(69.07±40.09)f0.90±0.23, suggesting that the study area is a tectonically inactive zone. The attenuation coefficient for high frequency waves increases with seismic activity. Further analysis on the relationship between QC(f) and the sampling depth reveals that big attenuation layers exist deep beneath the study area.