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Underwater Seismic Refraction
The Underwater Seismic Refraction (USR) testing is a complete seismic refraction method specifically designed for marine applications. One or more 12-channel hydrophone array with detectors at 2m intervals are deployed on the sea or river floor.
Seismic sources, that may be marine sparkers or small explosive charges in an environmental container, are placed on the floor at a range of offset distances from both ends of the detector array. First arrival travel-times are determined from digital recordings of the received seismic signals.
These are computer processed and interpreted and supplemented by computer ray-tracing. The entire system is moved along a profile by successively raising and lowering the system and shooting at pre-selected intervals. The USR system may be deployed from a small vessel.
Coffey Geotechnics provides a full professional and technical service for USR testing, including licensed shotfirers.
Applications:
- shallow rock and hard bottom conditions
- piling and offshore foundation assessment
- dredgeability studies
- thickness and nature of marine sediments
- shallow water and poor seismic reflection conditions
- sand/gravel resources.
