Technical Report No. 6
Leonard A. Palmer
This study developed instrumentation and techniques to be used for seismic exploration of groundwater in Hawaii. A three-stage field test of instruments and methods was conducted to determine their capability of recording and reproducing seismic data. Reproducibility was the main criterion to permit using certain signal analysis techniques. Multichannel explosive tests utilizing dynamite shots were carried out in Waimanalo, Oahu during the first stage of testing. The second stage was the use of a two-channel magnetic tape recorder converted to receive voice and up-hole geophone signals on one channel and seismic signals on the other channel. Stage three tested the use of a “thumper” acoustical source, seismic filters and timers developed for the project. The signals generated by explosives and recorded photographically were very reproducible, but this is a relatively expensive method and analysis is slow. Seismic data recorded on magnetic tape allows versatility in analysis of recorded signals reproduced either in wiggle or intensity contrast analog form. Sections can be selected for digital computer analysis. The findings from this pilot phase of seismic exploration for groundwater does not indicate that seismology would not be an appropriate tool for studying geological structure. Success in further work will be implemented by this preliminary work in solving instrumentation and the number of personnel of the Water Resources Research Center and the Hawaii Institute of Geophysics who have been trained.