Pressure records and vertical particle velocity records from dual sensor towed streamer data are transformed to the inline wavenumber domain. A series of scaling filters are applied to the transformed vertical particle velocity records at each inline wavenumber, wherein each of the series of scaling filters is calculated for a different cross-streamer wavenumber range and in blocks of inline traces in which all seismic events are approximately linear. The pressure spectrum and the scaled vertical particle velocity spectrum are combined to separate upgoing and downgoing wavefield components. The separated upgoing and downgoing wavefield components are inverse-transformed back to the time-space domain.