2021年玛多M_(S)7.4地震与2010年玉树M_(S)7.1地震前频谱特征分析

Spectral Characteristics before the 2021 Maduo M_(S)7.4 Earthquake and the 2010 Yushu M_(S)7.1 Earthquake

为进一步验证和完善使用频带变窄且向低频段偏移特征识别前震的判定依据,本文基于青海、甘肃等区域数字化测震台网记录的波形数据,对比分析2021年玛多7.4级地震前148 d发生的2020年12月24日玛多4.2级地震与2010年4月14日玉树7.1级地震前的4.7级地震快速傅里叶变换的频谱特征。结果显示,玛多4.2级地震频谱的频段较宽,优势频段为0~5.0 Hz,玉树4.7级地震频谱的频带变窄且向低频端偏移的特征较为显著,优势频段为0~1.5 Hz。对比分析认为,“频带变窄且向低频偏移”现象对识别直接前震有较好的效果,需重点关注中小地震出现频谱偏移后短期内(1~3个月)震源区附近强震发生的可能性。

In order to further test and improve the judgment basis for identifying foreshocks through the characteristics of "narrow frequency band and low-frequency migration",this paper compares and analyzes the FFT spectra of the Maduo M_(S)4.2 earthquake on December 24,2020,and the Yushu M_(S)4.7 earthquake on April 14,2010 based on the waveform data recorded by digital seismic networks in Qinghai,Gansu,and other regions.The results show that the frequency band of the Maduo M_(S)4.2 earthquake spectrum is wide,the dominant frequency band is O~5.O Hz.The frequency band of the Yushu M_(S)4.7 earthquake narrowed and shifted to the low-frequency end,the dominant frequency band of O~1.5 Hz.The comparative analysis shows that the "frequency band narrows and shifts to low frequency"phenomenon is effective for direct foreshock identification.In the future,it is necessary to focus on the possibility of strong earthquakes occurring near the source area in the short term(1~3 months)after the frequency spectrum shift of small and medium earthquakes occurring.