Spectrum Deviation Method of Identification of Foreshocks or Generalized Foreshocks and Its Applications  

作　　者：Yang Liming Mei Xiuping Jiang Jiajia 

机构地区：[1]Lanzhou Institute of Seismology,China Earthquake Administration

出　　处：《Earthquake Research in China》2016年第2期155-165,共11页中国地震研究（英文版）

基　　金：sponsored by the National Key Technology Support Program of China entitled "Application of Digital Seismic Technology to Mid-and Short-term Prediction of Strong Earthquake"(2012BAK19B02-01)

摘　　要：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 M_S4. 7 event which occurred before the Yushu M_S7. 1 earthquake on April 14,2010 and the M_S5. 3 event which occurred before the Yutian M_S7. 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.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 Ms5. 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 non- foreshock seismic spectrum of equivalent size. Therefore, this result can verify the validity of the spectrum deviation method.

关 键 词：Foreshocks or generalized foreshocks FFT mean square spectrumSpectrum deviation method 

分 类 号：P315[天文地球—地震学]