Method for seismic marine survey

Claim 1

A method of marine seismic prospecting comprising the steps of: establishing a bubble containing a high-pressure expanding volume of gas at a sufficient depth to prevent the gas from directly venting to the atmosphere; the initial expansion of said gas bubble generating in the water a desired initial acoustic impulse for subsequent reflection from the sub-bottom strata; said gas bubble subsequent to said initial expansion collapsing and again expanding to create in the water at least a first bubble acoustic impulse which also becomes reflected from said sub-bottom strata; detecting the reflected signals from said initial impulse and said first impulse; and detecting the unreflected acoustic impulses with at least one pressure detector assembly, said detector assembly comprising: (a) a housing having a flexible, pressure-transmitting wall defining a chamber; (b) a substantially incompressible dielectric liquid completely filling said chamber, (c) a detector probe completely immersed in said liquid, said probe comprising: a metallic housing, a quartz crystal mounted on an inner wall portion of said housing, an amplifier in said housing, and circuit means coupling said quartz crystal to the input circuit of said amplifier; and recording at a remote location the output signals from said amplifier, said output signals representing said unreflected acoustic impulses.

Claim 2

A method of marine seismic prospecting comprising the steps of: establishing a bubble containing a high-pressure expanding volume of gas at a sufficient depth to prevent the gas from directly venting to the atmosphere; the initial expansion of said gas bubble generating in the water a desired initial acoustic impulse for subsequent reflection from the sub-bottom strata; said gas bubble subsequent to said initial expansion collapsing and again expanding to create in the water at least a first bubble acoustic impulse which also becomes reflected from said sub-bottom strata; detecting the reflected signals from said initial impulse and said first impulse; and detecting the unreflected acoustic impulses with at least one pressure detector assembly, said detector assembly comprising: (a) a housing having a flexible, pressure-transmitting wall defining a chamber; (b) a substantially incompressible dielectric liquid completely filling said chamber, (c) a detector probe completely immersed in said liquid, said probe comprising: a metallic housing, a quartz crystal mounted on an inner wall portion of said housing, an amplifier in said housing, and circuit means coupling said quartz crystal to the input circuit of said amplifier; and recording at a remote location the output signals from said amplifier, said output signals representing said unreflected acoustic impulses.