Bedrock and Fracture Zone Delineation Using Different Near-surface Seismic Sources

To delineate the bedrock surface and a fracture zone intersected by a well at c. 50 m depth, a seismic survey was conducted using four different near-surface seismic sources. These were a 5-kg sledgehammer, a metal I-beam hit laterally, an accelerated weight drop and a prototype source tested for the first time called Udarnik. The Udarnik source has two hammers whose impacts are initiated by an electromagnetic force of the stable coil exciting its inner moving part. Two hammers separated by a distance of approximately 50 cm successively hit two contact plates mounted on the bottom of the source. The sweep length is adjustable and maximum 18 hits can be made per second. In this study, we compare the performance of every source used and present reflection seismic sections and tomography results from the high-fold (star-type acquisition was used) combined landstreamer and wireless recorder survey. Preliminary results indicate that bedrock was well delineated both on tomography results and stacked sections for all sources and some weak reflectivity is observed where the fracture zone is expected with most of the sources used showing the potential of the seismic methods for fracture zone imaging and near-surface characterization