The influence of near-seafloor low velocity layers on shallow marine seismic measurements

Detailed investigations of the influence of low velocity layers, especially gassy-mud sediments were made,<br>based on industrial seismic data from the southern baltic sea. More than a half of the Greifswalder- Boddenbay<br>is covered by such sediments. In these regions absorption of more than 90 percent, strong high frequency<br>singing, low frequency waves and travel-time anomalies up to 50 ms were found.<br>Large Problems results from this travel-time anomalies because of potential misinterpretation as tectonic<br>structures. To distinguish between real tectonic structures and travel-time anomalies we investigated traces<br>of different offsets. At large offsets a local surface caused travel-time anomaly will be observed two times in<br>this seismogram. Two different reasons for travel-time anomalies was found: gassy mud sediment at the sea<br>bottom and pleistocene channels.<br>Static corrections of travel-time anomalies due to gassy mud sediments can be done by using variations of<br>first break travel-times as correction time values.