Comparison Of Lower-Frequency (<Lo00 Hz) Downhole Seismic Sources For Use At Environmental Sites

In conjunction with crosswell seismic surveying being done at the Hanford Site in south-central Washington,<br>four different downhole seismic sources have been tested between the same set of boreholes. The four sources<br>evaluated were the Bolt airgun, the OYO-Conoco orbital vibrator, and two Sandia-developed vertical vibrators,<br>one pneumatically-driven, and the other based on a magnetostrictive actuator. The sources generate seismic<br>energy in the lower frequency range of less than 1000 Hz and have different frequency characteristics, radiation<br>patterns, energy levels, and operational considerations. Collection of identical data sets with all four sources<br>allows the direct comparison of these characteristics and an evaluation of the suitability of each source for a<br>given site and target.