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采用脉冲传播谱振幅比法、能量法和尾波法分别测定片麻岩破裂孕育过程中的Ｑ值变化．结果表明：谱振幅比法所得Ｑ值呈现相对平稳值—升高至甚高值（极大值）—回降—破裂的变化形式；能量法所得Ｑ值变化形态与上述相反，即平稳值—低值—回升—破裂；而尾波法所得Ｑ值，主频Ｑ值呈现相对高值—下降至低值（极小）—回升—破裂，与能量法Ｑ值变化大体一致．而对于高频（大于主频）Ｑ值则呈现平稳值—升高至极大值—回降—破裂．同时尾波振幅谱还表明：应力达７０％破裂应力后，首先是高频Ｓ波迅速减少（ＱＣ）变大），临近主破裂时主频Ｓ波则大幅度减少（ＱＣ回升），这可能是两种尾波ＱＣ变化形态不同的原因所致．而Ｐ，Ｓ波（初至波）振幅谱也表明，随着裂隙出现，Ｓ波频带变窄，高频成分迅速减少．即Ｓ波谱变化不同．这使采用不同方法所得的ＱＳ的变化特征不同
Pulse amplitude spectrum method, energy method and coda method were used to determine the change of Q value in the process of gneiss rupture. The results show that the Q value obtained by spectral amplitude ratio shows a relatively stable value - up to a very high value (maximum) - fallback - rupture changes; energy Q value changes in morphology contrary to the above, the steady value - Low value - rebound - rupture. However, the Q value and the fundamental frequency Q value of the coda wave presented a relatively high value - decreased to a low value (minimum) - rebounded - ruptured, which was generally in accordance with the Q value of the energy method. For high frequency (greater than the main frequency) Q values showed a smooth value - up to the maximum - fall - burst. At the same time, the coda wave amplitude spectrum also shows that the stress ruptures at 70%, firstly the rapid decrease of high frequency S wave (QC) becomes larger and the main frequency S wave decreases sharply near the main rupture (QC rebound) It is caused by the different cues of the two coda waves. The amplitude spectrum of P and S wave (first arrival wave) also shows that as the fissure appears, the S wave band narrows and the high frequency component decreases rapidly. That is, the spectrum of S varies. This makes the different characteristics of QS obtained by different methods