System for attenuation of water-column reverberations

An improved seismic reflection method for geophysical prospecting in water covered areas,

• said method being free of filter means including a deconvolution operation for changing the frequency content of any one of pressure-detecting and velocity-detecting elements,
• said method comprising the steps of
• A. generating a seismic wave for reflection from earth strata,
• B. positioning a pressure detector and a velocity detector substantially near water's bottom for detecting said water pressure and said water velocity and for generating signals representative thereof,
• C. detecting water velocity at a position substantially near the position of said pressure detector resulting from said seismic wave and generating a signal representative thereof, and
• D. generating an enhanced seismic reflection signal as a selected linear combination of said water pressure representative signal and the water velocity-representative signal, said enhanced seismic reflection signal being substantially free of at least downwardly-propagating components of reverberation of said seismic wave within the water, said enhanced seismic reflection signal-generating step includes the steps of
• i. scaling said water velocity-representative and water pressure-representative signals by multiplying at least a selected one of them by a scale factor dependent upon an acoustical impedance of a solid earth material at said water's bottom,
• ii. summing said scaled water velocity-representative and water pressure-representative signals to produce said enhanced seismic reflection signal, said enhanced seismic reflection signal being substantially free of downwardly-propagating and upwardly-propagating components of reverberation of said seismic wave within the water.

An improved system for seismic reflection prospecting in water covered areas,

• said system being free of filter means including a deconvolution operation for changing the frequency content of any one of pressure-detecting an velocity-detecting elements,
• said system comprising
• A. means for generating a seismic wave for reflection from earth strata,
• B. Pressure detection means disposed substantially near a bottom of said water for detecting a pressure associated with a resultant seismic wave and for generating signals representative thereof,
• C. particle velocity detection means disposed at a position substantially near said pressure detection means for detecting a particle velocity associated with said resultant seismic wave and generating a signal representative thereof, and
• D. enhanced seismic reflection means coupled with said pressure detection means and said particle velocity means for generating an enhanced seismic reflection signal as a selected linear combination of said water pressure-representative signal and the water velocity-representative signal, said enhanced seismic reflection signal being substantially free of at least downwardly-propagating components of reverberation of said seismic wave within the water,
• said enhanced seismic reflection means including
• i. means for multiplying at least a selected one of said pressure-representative and water velocity-representative signals by a scale factor dependent upon an acoustical impedance of a solid earth material at said water's bottom,
• ii. means for summing said scaled water velocity-representative and water pressure-representative signals to produce said enhanced seismic reflection signal, said enhanced seismic reflection signal being substantially free of downwardly-propagating and upwardly-propagating components of reverberation of said seismic wave within the water.