在前期研究的基础上，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，正常背景的中等震级地震事件频谱较宽，而具有前震或广义前震性质的中等震级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，且与非前震性同等震级地震频谱差异明显。

On the basis of previous research work，this paper proposes a foreshock or generalized foreshock recognition spectrum deviation method． As a judge index，the spectrum of moderate earthquake events is wide for ordinary seismicity，while moderate earthquake with the nature of foreshocks or generalized foreshocks has the characteristics of a narrow frequency band，and it is deviated to the low frequency． The root cause may be related to metastable extension in the source or related area before main shock rupture or to regional fragmentation damage，crack nucleation process． An earthquake with MS7． 1 occurred on April 14，2010，in Yushu，Qinghai Province with a foreshock event with MS4． 7 and a magnitude 7． 3 earthquake happened on February 12， 2014，in Yutian，Xinjiang with a foreshock event with MS5． 3． The calculation results of these two foreshocks show that the spectrum of foreshocks all had deviations，and they are quite different from non-foreshocks seismic spectrum of equal size． Therefore，this result can verify the validity of the spectrum deviation method．

国家科技支撑项目专题“数字地震技术在强震中短期预测中的应用”(2012BAK19B02-01)资助