三瞬剖面法在人工地震测深中的应用研究

本文简述了Hilbert变换原理及三瞬剖面的制作方法(又称复数道分析法),并对理论合成地震记录进行了处理,得到三瞬剖面,分析了这些剖面的特征以及利用这些特征进行地震解释的可能性,对人工地震测深资料进行处理,着重探讨了地震记录中来自中地壳低速层上下界面的反射波,P_3~0,P_4~0在剖面上的反映,结果发现;(1)P_3~0在相位剖面上出现相位反转,从波的动力学特征上证实了P_3~0是来自低速层预界面的反射波;(2)P_3~0的频率在频率剖面上相对稳定,大致在12—14HZ之间,而P_4~0的频率略小,一般在11—13HZ之间,这说明地震波经过低速层后,频率有所下降;(3)P_3~0的振幅在振幅剖面上表现出稳定的幅值,P_4~0则变化比较大,来自Moho面的反射波P_4~0包络明显。基于以上结论,作者认为在人工地震测深资料的数字处理中,应用三瞬剖面法,可从地震波的动力学特征上为判别地壳内低速层的存在提供有意义的证据。

THE APPLICATION OF 3-MOMENT-SECTION METHOD TO DSS DATA PROCESSING

In this paper, the Hilbert transform and way of making 3-moment-section are introduced briefly, and the synthetic seismograms are processed, so as to obtain the 3-moment-section. By analysing those section characters and the probability of making seismic interpretations with those characters, the DSS data have been processed. Particularly, the reflection wave P30 and P40 coming from upper and lower boundaries of lower velocity layer in the mid crust are studied. It can be seen from-the obtained results that. (1) From a dynamic point, the phase reversal appeared on the P30 phase section confirms that P30 is a reflection wave from the upper boundary; (2)P30 frequency is relatively stable on the frequency section, ranging approximately 12-14 Hz, whereas P40 freqveny is smaller ranging 11-13 Hz. This shows a frequency decrement of seismic waves through lower velocity layer; (3) P30 amplitude shows stable values on the amplitude seetion;P40 amplitude varies comparatively great; and PM0 reflected from Moho has a clear envelope. Based on the above conclusions the authors hold that, from a dynamic point the application of 3-moment-section method to DSS data processing can present significant evidences for evaluating the existence of lower velocity layer in the crust.