利用地震转换波探测地壳、上地幔构造试验

当远震P波通过地壳、上地幔速度界面时,除了产生PP型折射波,还产生一系列PS型折射转换波.这类PS转换波与初至P波之间的到时差,可用来测定地壳和上地幔构造. 转换波测深法首次在我国鲁西夏津—高唐地区和京西昌平地区进行了试验应用.为提高转换波震相识别的可靠性,在资料分析中采用了偏振滤波的方法.工作结果获得了上述两地区的深部构造剖面图.转换波法与爆炸地震法所得结果之对比表明,两者的主要界面基本一致.

AN EXPERIMENTAL STUDY OF THE STRUCTURE OF THE EARTH'S CRUST AND UPPER MANTLE BY CONVERTED WAVES

When P waves from distant earthquakes meet a velocity discontinuity in the earth's crust and upper mantle,they give rise to a series of converted PS waves besides PP refracted waves. The difference of arrival times between such PS and PP waves can be used to determine the structures in the earth's crust and upper mantle.For the first time,method converted waves from distant earthquakes have been tried in the Shiahjin-Gautarng （夏津-高唐） region of western Shandung,Province and in the Changpirng （昌平） area west of Peking.Polarization filtering was employed to analyze the seismic data in order to increase the reliability in identifying the PS phases. As a result,the crustal structures in these two regions have been found and it is indicated that the main deep discontinuities thus obtained are essentially the same as those determined by deep seismic sounding experiments using explosions.