折射波法探测断层的模拟试验——记录图的特征

用折射波法对断层进行勘探的实际工作中,不仅观察到上、下盘的正常折射波及棱上的绕射波,而且还可以看到因绕射、透过所产生的一些次生异常波.这些波郁同时在记录上出现,并构成一幅复杂的波形图.如果不能一一地识别它们,并掌握它们的运动学及动力学特征,就无法正确地识别及解释断层.以往一些文章多半讨论板状介质边缘上的绕射现象,而未涉及上、下盘同时存在时,折射法记录上可能出现的次生绕射、折射波. 本文为了解决这一问题,利用了超声波脉冲地震模拟仪进行了实验,对不同大小断距情况下的折射异常波及次生波进行了研究,回答了有关断层勘探中必须阐明的一些问题.

A MODEL EXPERIMENT OF PROSPECTING OF FAULTS BY THE REFRACTION METHOD——CERTAINF EATURES ON THE SEISMOGRAMS

In the prospecting of faults by the refraction method, not only the ordinary refracted waves from the downthrow and upthrow sides of a fault and the diffracted waves from the fault plane are observed but also certain secondary waves resulted from diffraction and transmission can be recorded on the seismograms. The whole set of waves constitutes a very complicated picture of the seismograms. If their kinematic and dynamic characteristics are not capable of being recognized and distinguished, it would be very hard to interpret the results of fault prospecting by the refraction method. In most of the previous literatures, only the diffraction phenomena on the edge of a plate have been discussed while the secondary waves by diffraction and refraction appearing possibly on seismographie records when both the upthrow and downthrow sides of the fault are present have been neglected.In this paper, the results of a model experiment using ultrasonic impulses are described and studies made in connection with the prospecting of faults by the refraction method of different throw magnitudes, the recorded anomalous refracted waves and secondary waves.