2014年秭归M4.7、 M4.5地震序列与2017年秭归-巴东M4.3、 M4.1地震序列对比研究

摘要

This paper,which compares geological background structure,earthquake sequence and various source parameters,comes to the following conclusions:1) The 2014 M4.7 and M4.5 earthquakes are related to the northern section of the Xianniishan fault microscopically and the nearest fault to the M4.3 and M4.1 earthquakes in 2017 is the Zhoujiashan-Niukou fault.2) The M4.7 and M4.5 earthquakes in 2014 are rich in aftershocks with more than 500 aftershocks recorded.Among them,aftershocks of magnitude 2 and above are recorded 5 times with the maximum aftershock of M2.9 (ML3.5),with aftershocks lasting more than one month.The 2017 M4.3 and M4.1 earthquakes recorded only 160 aftershocks,including 3 aftershocks above level 2 and M2.6(ML3.3) with the largest aftershocks lasting about 20 days.3) The best focal depth of the M4.7 and M4.5 earthquakes in 2014 is about 7 km.In 2017,the source depth of M4.3 and M4.1 is 3～5 km.4) The dominant and corner frequencies of the main shocks in 2014 M4.7 and M4.5 earthquakes are not high;the dominant frequency is 1.5～8.0 Hz and the corner frequency is 3.0-8.0 Hz.Levels of the frequency spectrum of M4.3,M4.1 earthquakes in 2017 are mainly distributed at the dominant frequency and the corner frequency is low,suggesting fall or shallow landslide type characteristics.%从地质背景构造、地震序列、震源参数等方面对2014年秭归M4.7、M4.5地震与2017年秭归-巴东M4.3、M4.1地震进行对比分析,得出如下结论:1)2014年M4.7、M4.5地震从微构造上与仙女山断裂北段有关,2017年M4.3、M4.1地震震区最近断裂为周家山-牛口断裂.2)2014年M4.7、M4.5地震余震丰富,记录到的余震500余次,其中2级以上余震5次,最大余震M2.9(ML3.5),余震活动持续超过一个月;2017年M4.3、M4.1地震只记录到余震160多次,2级以上余震3次,最大余震M2.6(ML3.3),余震活动持续20 d左右.3)2014年M4.7、M4.5地震的最佳震源深度约为7 km,2017年M4.3、M4.1地震的震源深度为3～5km.4)2014年M4.7、M4.5地震主震优势频率和拐角频率均不高,优势频率为1.5～8.0 Hz,拐角频率为3.0～8.0 Hz,这种频谱特征可能是水库诱发构造地震的特性之一;2017年M4.3、M4.1地震优势频率不高,拐角频率亦较低,有近似陷落或浅表滑坡的特征.