Soils have strange acoustic behavior.
Where practical, seismic sources are buried under the weathered zone, but the receivers are almost always on the surface. About the only time you may encounter buried receivers is in a marshy area. There field operations are so difficult that you will have many fewer receivers than normal. A source of much difficulty is that soils are severely laterally inhomogeneous. It is not rare for two geophones separated by 10 meters to record quite different seismograms.