Marine surface wave investigation in a harbour in southern Sweden

A marine surface wave seismic investigation was performed in order to characterize the sediments and bedrock in Ystad harbor, southern Sweden. The dispersive nature of Sholte waves was analyzed and fundamental mode dispersion curves extracted. Using inverse modelling a few layer shear wave velocity, Vs, profile was successfully retrieved to a depth of 5-10 m below sea bottom. The seismic results were confirmed with result from geotechnical probing. The measurements were made with a 12-channel neutral buoyancy streamer with 2 m hydrophone separation. A small number of led plates were attached to the streamer in order to make it sink and for each measurement the ends of the streamer were fixed on the bottom using small concrete blocks. The streamer was pulled up on the vessel before moving to the next measurement position. As energy source a small amount of explosives was detonated on the sea bottom with the shot positioned at 15-30 m distance from the nearest hydrophone and inline with the streamer. The production rate of this approach was 30 measurements in one field day, which should be compared to the 1 or 2 geotechnical soundings that can be achieved at the same time.