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剪切波分裂应用于地震预报中的3个主要困难是:(1)如何自动定量识别剪切波快慢波到时;(2)用以认识其基本特征的震例太少;(3)因各次地震的复杂性,对所给剪切波分裂结果难以给出恰当的解释。本文研究了1988年11月22日甘肃肃南5.7级地震过程剪切波分裂的特征。所用资料为1988年8月到1990年8月中法合作张掖数字台网的记录。通过对张掖～肃南地区地壳结构模型的研究,确认了所用各次地震的真实出射角基本上位于剪切窗附近。联合使用本文提出的最大特征值法、波形识别算子法和最大似然法,定量确定了剪切波快、慢波到时。结果表明:1988年甘肃肃南5.7级地震前后,快、慢波时间延迟呈现了减小(1988年10月至11月22日)～发震～恢复(主震后)的形态,其基本形态类似于1990年天祝—景泰地震过程。综合分析了地震剪切波分裂的时间进程和空间动态分布,用EDA模式和组合模式解释了出现的特征,认为此次地震出现了具有物理意义的剪切波分裂前兆。
The three main difficulties in the application of shear-wave splitting to earthquake prediction are: (1) how to automatically and quantitatively detect the arrival of shear waves at the time of arrival; (2) the number of earthquakes used to recognize their basic features is too small; (3) The complexity of various earthquakes makes it difficult to give proper explanations for the results of shear-wave splitting. In this paper, the characteristics of shear-wave splitting during the M5.7 Sunan Gansu earthquake on November 22, 1988 are studied. The information used is from August 1988 to August 1990, the record of Sino-French cooperation Zhangye digital network. Through the study of the crustal structure model in Zhangye ~ Sunan area, it is confirmed that the real exit angle of each earthquake used is basically located near the shear window. Combined with the maximum eigenvalue method, the waveform recognition operator method and the maximum likelihood method proposed in this paper, the shear wave fast and slow wave arrival time are quantitatively determined. The results show that the time delays of fast and slow wave show a pattern of decreasing (from October 1988 to November 22, 1988) ~ seismogenic ~ recovering (main shock) before and after the M5.7 Sunan earthquake in 1988, with the basic morphology Similar to the 1990 Tianzhu - Jingtai earthquake process. The time course and spatial dynamic distribution of seismic shear wave splitting are comprehensively analyzed. The characteristics of the occurrence of seismic shear wave splitting are explained by EDA mode and combination mode. It is considered that the physical shear wave splitting precursor appears in this earthquake.