Determination of reflectivity and water depth for marine seismic exploration

In marine seismic exploration which includes:

• firing at least one source in an array of sources towed by a marine vessel,
• recording seismograms representing the reflected seismic pulses,
• measuring the water bottom reflectivity and the water depth from the recorded seismograms,
• converting the measurements of reflectivity and water depth into a time domain operator representative of the inverse of the reverberaion distortion in the water layer between the water bottom and water surface, and
• thereafter firing said array of sources in groups such that the acoustic pulses from each of said sources combine to produce a resultant acoustic pressure wave having said time domain operator characteristic in its travel to and from the subsurface formation,
• the improvement wherein said measuring comprises the steps of:
• generating the zero lag auto-correlation coefficients of a window of said seismogram,
• generating the auto-correlation coefficients of said window with a lag of n time samples,
• generating the auto-correlation coefficients of said window with a lag of 2n time samples,
• repeating the foregoing for various values of n,
• combining the auto-correlation coefficients generated for each value of n, and
• selecting the n producing the minimum in the combined auto-correlation functions as being representative of water depth.