A method to enhance the energy of deep seismic signals by using low-frequency deghosting filter
The presence of ghost waves suppresses the low-frequency energy of signal acquired in marine seismic exploration, while deep structures of the earth mainly correspond to the low-frequency signal components, thus, it is of great significance to improve the low-frequency components suppressed by ghost waves for the detection of deep structures. One of the key parameters of ghost wave suppression is the arrival time difference between the ghost wave and the primary reflected wave, and its accuracy directly affects the effect of ghost wave suppression. Due to the influence of factors such as undulating sea surface, rugged seabed, depth change of reflective layer, and distribution of inhomogeneous media, the arrival time difference between the ghost wave and the primary reflected wave can often not be accurately estimated, resulting in the failure to achieve good results in ghost wave suppression. In this paper, based on the characteristics of the deghosting filter, a filter that does not disturb the high frequency and only improves the low frequency is designed to bypass the suppression of the ghost wave and only focus on the energy improvement of the low-frequency signal. The results of model tests show that the waveform processed by the proposed method is morphologically close to the primary reflected waveform without ghost wave interference. Moreover, the lower the dominant frequency of the seismic signal and the smaller the sinking depth of the towing cable, the stronger the energy enhancement effect of this method on the low-frequency signal. A test applied in the deep reflection seismic profile of the South China Sea has also attained good performances.