Acquiring shallow reflection data requires the use of high frequencies, preferably accompanied by broad bandwidths. Problems that sometimes arise with this type of seismic information include spatial aliasing of ground roll, erroneous interpretation of processed airwaves and air-coupled waves as reflected seismic waves, misinterpretation of refractions as reflections on stacked common-midpoint (CMP) sections, and emergence of processing artifacts. Processing and interpreting nearsurface reflection data correctly often requires more than a simple scaling-down of the methods used in oil and gas exploration or crustal studies. For example, even under favorable conditions, separating shallow reflections from shallow refractions during processing may prove difficult, if not impossible. Artifacts emanating from inadequate velocity analysis and inaccurate static corrections during processing are at least as troublesome when they emerge on shallow reflection sections as they are on sections typical of petroleum exploration. Consequently, when using shallow seismic reflection, an interpreter must be exceptionally careful not to misinterpret as reflections those many coherent waves that may appear to be reflections but are not. Evaluating the validity of a processed, shallow seismic reflection section therefore requires that the interpreter have access to at least one field record and, ideally, to copies of one or more of the intermediate processing steps to corroborate the interpretation and to monitor for artifacts introduced by digital processing.

Seismic reflection surveys were used to follow the drawdown in a shallow aquifer during a pumping test. Using severe analog low‐cut filters and 1/4‐m geophone spacings, 335 Hz reflections were obtained from the top of the saturated zone 2.7 m deep. The reflections moved down in time as the saturated zone dropped in response to pumping. The dominant frequency and bandwidth both dropped during pumping indicating a more diffuse reflecting boundary. Slight pullups of reflectors at specific locations on the CDP sections may indicate a higher elevation of the capillary fringe and therefore finer sediments in those locations. Other potential applications of this technique include mapping cones of depression and detecting and delineating perched‐water tables.

The results of a seismic reflection profiling exercise are strongly dependent upon parameters used in field recording. The choice of parameters is determined by objectives of the survey, available resources, and geologic locality. Some simple modeling and/or a walkaway noise survey are helpful in choice of field parameters. Filtering data before analog‐to‐digital conversion in the field can help overcome limitations in the dynamic range of the seismograph. Source and geophone arrays can be used to a limited extent in high‐resolution surveys to help attenuate ground roll. Proper planting of geophones can be an important factor in obtaining the flattest spectral response. Various seismic energy sources provide the flattest spectral response. Various seismic energy sources provide different spectral character and varying degrees of convenience and cost.