本文提出用于地下成像无源地震方法的分析，在该方法中应用环境地震噪声作为地下散射体的照明源。
An analysis of a passive seismic method for subsurface imaging is presented in which ambient seismic noise is employed as the source of illumination of subsurface scatterers.
而日本的激光干涉管直接修建在地下并维持极低的温度，以降低散射带来的波动。
The interferometer in Japan is being built underground and will be kept at extremely low temperatures to minimise stray vibrations. There are also plans to refine existing experiments.
本文论述了FD-TD法用于计算地下浅层目标的电磁散射问题。
The electromagnetic scattering by buried objects in dispersive media is calculated by FD-TD method.
地下二维散射问题是地下电磁勘探技术的基础。
Two-dimensional electromagnetic scattering from an underground cylinder is the foundation of underground EM prospecting.
分别计算了典型地下目标的散射波形和波形堆积图。
The scattering pulses and the wiggle traces are given for several typical buried objects.
利用放射性源的伽马射线轰击井眼周围的岩石，通过对反散射伽马射线计数，可以计算出地下岩石的密度。
A radioactive source is used to bombard the rocks surrounding the wellbore with gamma rays. By counting the backscattered gamma rays, the density of the subsurface rock can be computed.
利用放射性源的伽马射线轰击井眼周围的岩石，通过对反散射伽马射线计数，可以计算出地下岩石的密度。
A radioactive source is used to bombard the rocks surrounding the wellbore with gamma rays. By counting the backscattered gamma rays, the density of the subsurface rock can be computed.
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