Abstract: A method for reducing the effects of reverberation on noisy seismic wavefields recorded from within a moisture-laden environment. The wavefield manifests itself as a pressure signature and a velocity signature that contains an embedded nose signature. The pressure signature is adaptively filtered and subtractively combined with the velocity signature to isolate a nearly pure noise signature. The nearly pure noise signature is added back to the original velocity signature with opposite sign to clear away the embedded noise, leaving a refined velocity signature. The refined velocity signature iteratively is scaled and summed with the pressure signature, incrementing the scale factor at each iteration and autocorrelating the sum. A coefficient of convergence is calculated after each summation. The coefficient of convergence that most closely approaches unity identifies the preferred scale factor.

Abstract: Marine seismic data is gathered using a cable towed behind a cable having a slanted orientation in the water. The recorded data is processed to remove the time offset in the recorded data of seismic signals arriving at the cable at varying plane wave angles. In a preferred embodiment of the invention, the recorded data is then processed to align the primary signals, thereby misaligning the ghost signals. The data is also processed to align the ghost signals, thereby misaligning the primary signals. The two resulting data sets may then be summed.

Abstract: The invention is a method of reducing phase distortion in a detected seismic signal resulting from Doppler shifting of the transmitted signal. An operator is convolved with the seismic data to correct the dispersion. The operator is determined for the particular transmitted signal and boat speed. The operator is normally determined in the frequency-wave number domain. The seismic data may be transformed to the frequency-wave number domain for performing the convolution. The transformed data may then be transformed back to the time-space domain. Alternatively, the determined operator may be transformed to the time-space domain and the convolution performed in that domain.

Abstract: The invention is a method of shaping the spectrum of a seismic source signature. Energy is concentrated in the range below a selected frequency and attenuated in the range above the selected frequency by activating a plurality of sources asynchronously within a time window of selected duration. In a preferred embodiment, the frequency spectrum is smoothed by firing a second plurality of sources within a second time window having a time delay from the first time window equal to substantially the time between the initial firing of a source and the first positive zero-crossing of the signature.

Abstract: The far-field pressure signature of an air-gun array is derived from near-field measurements. An array of air guns is deployed in the water at a desired depth. A hydrophone is suspended in the middle of the array at the same depth so that the guns are equidistant from the hydrophone. The lateral spacing between the guns and the sensor is much less than the water depth of the guns. Having fired the guns, the ghost reflection amplitude in the near field will be much less than the amplitude of the direct arrivals and can be ignored. The far-field signature is determined by inverting the observed pressure signature, delaying it in proportion to array depth and adding the inverted, delayed signature back to the original signature.