Final answer:
Sub-surface surveys often utilize 3D seismic surveying, using closely spaced seismic data to create detailed cross-sections of the subsurface, allowing for identification of geological features.
Step-by-step explanation:
The method that sub-surface surveys often use is 3D seismic surveying. This technique involves collecting seismic data along closely spaced parallel lines, which are then processed and interpreted as a three-dimensional volume of data known as seismic cubes. The process helps geologists and surveyors to visualize cross-sections through an area under study. Modern seismic surveys feature seismic traces spaced about 12.5 meters apart. These surveys enable identification of rock types, deformation features, and the potential presence of water or petroleum, by analyzing the patterns of reflectivity from sound waves sent into the subsurface. Additionally, methods such as LiDAR use wavelength reflections to produce detailed images of topography, aiding in the study of geographic and archaeological features.