三峡库区仙女山断裂周缘地震类型特征识别

Feature identification of earthquake type occurred around the Xiannvshan fault in Three Gorges Reservoir area

为识别仙女山断裂周缘发生的构造地震、矿震、塌陷地震特征,基于集合经验模态分解时频分析方法(EEMD)对地震波形信号进行了分解,通过信号的IMF分量的时频谱和边际谱分析了其差异。结果表明:①构造地震的时频谱频率在0~40 Hz均有分布,频率成分复杂,边际谱集中在0~20 Hz;②矿震时频谱在0~30 Hz均有分布,频率成分相对简单,但在地震波幅值变化最大的区域存在20~30 Hz的频率成分空白区,边际谱存在一个0~5 Hz的主频带和2 Hz左右的主频;③塌陷地震时频谱频率成分分布在0~30 Hz,在Pg波到达前存在0~5 Hz左右低频区域,边际谱的主频带和主频集中在0~3 Hz和1 Hz。该研究成果可以作为识别构造、矿震、塌陷地震事件的判别依据。

In order to study and identify the characteristics of tectonic earthquakes,mine earthquakes and collapse earthquakes around the Xiannushan Fault in the Three Gorges reservoir area,the different types of seismic waveform signals were decomposed based on the ensemble empirical mode decomposition(EEMD)time-frequency analysis method.The time-frequency spectrums and the marginal spectrums of the IMF components were obtained and their main differences were analyzed.①The frequency of the time-frequency spectrum of tectonic earthquakes were distributed in the range of 0~40 Hz,and its frequency components were complex;the marginal spectrums of the tectonic earthquakes were concentrated in the range of 0~20 Hz.②The frequency band of the time-frequency spectrum of the mine earthquakes were distributed in the range of 0~30 Hz,and the frequency components were relatively simple.However,there were a 20~30 Hz frequency component blank area in the areas where the amplitude of mine seismic waves changed the most.There were a dominant frequency band with 0~5 Hz and dominant frequency with~2 Hz.③The frequency components of the collapse earthquakes time-frequency spectrum were distributed in the range of 0~30 Hz,and there were a low frequency region which ranged from 0~5 Hz before the Pg waves arriving.The dominant frequency bands and dominant frequency of the marginal spectrum of the collapse earthquakes were concentrated in the range of 0~3 Hz and 1 Hz.The research results above could be the basis for identifying the important features of tectonic earthquakes,mine earthquakes and collapse earthquakes.