安徽霍山窗重复地震尾波Qc值变化研究

本文用波形互相关方法识别霍山窗重复地震对,进一步在重复地震对中搜索重复地震序列.人工挑选了一条时间在上覆盖2009年且时间分布相对理想的由8个重复地震组成的重复地震序列(Repeating Earthquake Series, RES).挑选1个重复地震作为参考对象,使用前人提出的滑动窗口谱振幅比方法计算其它7个重复地震与该地震的尾波Q_c^-1值的变化量ΔQ_c^-1,结果发现在2009年的3次重复地震尾波Q_c^-1值的变化量ΔQ_c^-1比2008年和2010年有明显增大,即尾波Q_c^-1从2009年开始出现明显降低,2010年后恢复;若换算成Q_c值的变化其增幅可达11%~21%.然而在2009年霍山窗及附近地区并未发生中强地震,而是伴随尾波Q_c值增加出现了小震活动增强的现象.结合地球动力学知识和前人对中国大陆东西部中强地震活动特征及时间关系的研究结果,认为霍山窗重复地震尾波Q_c值的变化与前人研究的震前地震孕育导致的尾波Q_c值变化有所不同,前者可能是受到大陆西部物质东移和应力向东传递这种外部因素的影响导致霍山地区地壳应力的变化,因而引起尾波Q_c值的变化.

Study on variation of seismic coda Qc value of repeating earthquake series in Anhui “Huoshan Seismic Window”

In this paper, we identified repeating earthquake doubles in Huoshan Seismic Window in Anhui province using waveform cross-correlation method, and searched out Repeating Earthquake Sequences (RES) from these earthquake doubles. We picked a good RES which are composed of 8 repeating earthquakes occurred in the years from 2009, chose one event as reference object, and calculated the differential variation of coda Q_c^-1 of other 7 repeating earthquakes with the reference one using Moving Window Spectral Amplitude Ratio method, which was first proposed by Richard (1996). The result indicated that the RES coda Q_c^-1 exhibited an obvious decrease from 2009 and returned to normal level in 2010. In other words, the RES coda Q_c increased from 2009 with an amplitude about 11%~21%. However, there was no moderate or strong earthquake during 2009 in and around Huoshan Seismic Window, but the seismicity of small earthquakes enhanced in 2009 instead. Based on geodynamical knowledge and the previous studies on the correlation between the great earthquake activity in West China and strong earthquake activity in North China, we consider that the variation of RES coda Q_c^-1 during 2009 could not be attributed to the developing process of a large earthquake, but probably have been influenced by some external factors such as the western continental material eastward movement and the stress transferring, and hence giving rise to the increase of coda Q_c.