Comparison of Low-Energy Seismic Sources in Till

Low-energy sources were field tested in a region of glacial till in southwestern Ohio. A 12-fold CDP line was run using the Mini-Sosie method with three sizes of earth tampers. A portion of the same line was shot using three explosive types in shallow holes. Two of the explosive types were 0.15 kg and 0.23 kg conventional two-component mixtures. The third used 0.23 kg of the same mixture but it was formed into a shaped charge by placing a copper cone in the bottom of the bottle containing the explosive. The Mini-Sosie sections were similar but the smallest tamper gave the best signal-to-noise ratio and reflection continuity. The explosive sections were similar to each other but different from the Mini-Sosie records due to processing differences. The best section by any of the methods was obtained with the shaped charges. The reason is better high-frequency penetration through the till into the rock and less surface wave generation.