A hybrid method for strong low-frequency noise suppression in prestack seismic data

• A low-frequency cascade filter for strong noise suppression in prestack gather
• Aim at swell noise, flow noise, tug noise and seismic interference noise
• Effectively attenuate strong amplitude noise while preserve signal down to 2 Hz
• Adaptive spike-detecting median filter with trace rearrangement technique

Low-frequency components are important portion of seismic data in exploration geophysics, and have great effects on seismic imaging of deep subsurface and full waveform inversion. Unfortunately, seismic data usually suffers from various kinds of noises and has low signal to noise ratio (SNR) in low-frequency band, although this situation has been improved by developments of acquisition technology. In this paper, we propose a low-frequency cascade filter (LFCF) in Fourier domain for strong low-frequency noise suppression in prestack gathers. LFCF includes a 1D adaptive median filter in f–x domain and a 2D notch filter in f–k domain, which is able to process high-amplitude swell noise, random noise, and seismic interference noise. We employ traces rearrangement and spike-detection mechanisms in adaptive f–x median filter, which can handle strong noise specifically, such as wide-spreading swell noise and tug noise. And a notch filter in f–k domain is designed to separate reflection signal and random noise by different apparent velocities. Through these means, our method can effectively attenuate low-frequency random and coherent noise while simultaneously protect the signal. Experiments on synthetic example and field data are conducted, and the results demonstrate that our method is practical and effective and can preserve signal down to 2 Hz.