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前震或广义前震识别的频谱偏移法及其应用研究
杨立明 梅秀苹 姜佳佳
中国地震局兰州地震研究所, 兰州市东岗西路450号 730000
摘要:
在前期研究工作的基础上,本文提出了一种前震或广义前震识别的频谱偏移法。其判定指标为,正常背景的中等地震事件频谱较宽,而具有前震或广义前震性质的中等地震具有频带变窄且向低频端偏移集中的特征。究其根源可能与强震前震源区或主震相关区域亚稳态扩展破裂或区域介质破碎损伤、裂隙扩展成核等过程有关。对2010年4月14日青海玉树7.1级、2014年2月12日新疆于田7.3级等地震前震的计算结果显示,2次前震的频谱都发生了偏移,与非前震性同等震级地震频谱差异明显。
关键词:  前震或广义前震  FFT均方谱  频谱偏移法
DOI:
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基金项目:
Spectrum Deviation Method of Identification of Foreshocks or Generalized Foreshocks and Its Applications
Yang Liming,Mei Xiuping,and Jiang Jiajia
Lanzhou Institute of Seismology,China Earthquake Administration,Lanzhou 730000,China
Abstract:
Based on previous research work,we present a spectrum deviation method to recognize a foreshock or generalized foreshock in this paper. The criterion to determine whether an event is a foreshock is a wide spectrum for an ordinary event,however,a moderate earthquake with foreshock or generalized foreshock has the characteristics of a narrow frequency band,and it deviates to the low frequency. It may be explained by metastable extension in the rupture source or related area of the main shock or regional fragmentation damage and crack nucleation process. The calculation results of two foreshocks,the MS4. 7 event which occurred before the Yushu MS7. 1 earthquake on April 14,2010 and the MS 5. 3 event which occurred before the Yutian MS7. 3 earthquake on February 12, 2014,show that the spectra of foreshocks shift,and they are quite different from the nonforeshock seismic spectrum of equivalent size. Therefore,this result can verify the validity of the spectrum deviation method.
Key words:  Foreshocks or generalized foreshocks  FFT mean square spectrum  Spectrum deviation method