Pacific Coastal & Marine Science Center
Coastal and Marine Earthquake Studies
|Cascadia Earthquakes & Tsunami Hazard Studies
USGS Equipment Used on F.S. Sonne
Multichannel seismic reflection profiling requires a streamer containing many hydrophones for each channel recorded. This picture shows the spool that deploys the USGS streamer (a hydrophone cable several km long) installed on the fantail of R/V Sonne. The streamer is coiled on the spool and is shown covered with a tarp in the photo. It is deployed while the ship is underway by slowly turning the spool and feeding the streamer off the stern of the ship.
The sounds recorded using the streamer are generated by compressed air guns. The guns fire approximately once every minute. The sound waves produced travel through the water and layers of the earth and back up to the streamer. Special computers and software allow the seismic data to be used to make images of the structure of the earth. Geologic structures are known to be the locations of earthquakes in other areas.
This is a picture of USGS technicians Walt Olson, foreground, and Hal Williams, installing the airgun system on Sonne in San Francisco.
Seismic data from the streamer is recorded aboard the ship on magnetic tape using specialized electronics, computers and software. USGS seismic recording equipment was installed on R/V Sonne by Marine and Coastal Surveys Marine Facility personnel including Bill Robinson.
Text by Guy Cochrane, photographs by Hank Chezar