物理模型实验中一种特殊震相的分析讨论

Analysis and research on an special wave in model experiment

在双层物理模型的两分量超声波实验中,发现了一种特殊震相.用各种常规震相难以解释其运动学特征,它不符合斯奈尔定律所表述的首波、反射波、边界反射波和转换波等震相的运动学特征.其同相轴的时距关系类似于常规首波,但没有临界角,只出现在水平分量剖面上.我们对该震相的产生机理提出了假设:在近于垂直入射条件下,入射波遇到阻抗差异很大的界面时,就可以在该界面滑行,在滑行波中除纵波外,还有大部分能量转换成横波—特殊震相.此假设较合理地解释了模型实验中出现的特殊震相的运动学特征.

An special wave is found in a two-component ultrasonic experiment of a two-layer physical model. Its kinematical features are different from those of familiar waves such as head wave, reflected wave, boundary reflected wave and converted wave, whose kinematical behaviors can be described by SnelPs law. Its time-distance curve is similar with that of head wave, while it has no incident angle and can only be observed in horizontal component records. Based on detailed analyses and discussions, the unidentified wave is guessed to be S-wave converted from energy of P-waves sliding along strong impedance interface when a wave hit the interface with vertical or near vertical incident angle. ＇This hypothesis can interpret kinematical features of the special wave reasonably.