Geophones on a board

We examined the feasibility of using seismic reflections to image the upper 10 m of the earth’s subsurface quickly and effectively by attaching geophones to a wooden board at 5-cm intervals. The shallow-seismic-reflection information obtained was equivalent to control-test data gathered using classic, single-geophone plants with identical 5-cm intervals. The results were surprising: We found little intergeophone interference in response to our use of a high-resolution, .22-caliber-rifle seismic source at offsets of a few meters. Furthermore, we noted very little difference between the 60-ms intra-alluvial reflection obtained from the standard geophone plants and the reflection obtained from the board-mounted geophones. Amplitude spectra were nearly identical for geophone data collected with and without the board. The results suggest that deploying large numbers of closely spaced geophones simultaneously—perhaps even automatically— may be possible. Should this method of planting geophones prove practical after further testing, the cost effectiveness of very shallow seismic-reflection methods might be improved. The “board” technique also may be useful at greater depths and in broader applications, e . g . , petroleum exploration, in which geophones are sometimes bunched together tightly.