Air blast attenuation by combining microphone and geophone signals in the time-frequency domain
Alejandro David Alcudia León, Robert R. Stewart
Microphone data have been recorded during land seismic operations to give air pressure measurements in proximity to the geophones. Air pressure and seismic data can be combined to attenuate air-related noise from seismic records. We have developed a combination method in the time-frequency domain with the aid of the Gabor transform, a type of localized Fourier transform. The basic idea behind this method is that a nonstationary filter can be designed in the time-frequency domain, provided that a signal can be reconstructed from a modified version of its time-frequency decomposition. A mask function is constructed from the microphone Gabor spectrum by thresholding its Gabor coefficients. Then, multiplying the geophone Gabor spectrum with the mask function achieves a deterministic cancellation of the associated air pressure component in the seismic signal. In our experiments, the largest noise signal measured with the microphones is the air blast. Therefore, at this point of the research the Gabor transform method is largely restricted to air blast attenuation. We have successfully applied this methodology to a number of common shot gathers from the Pikes Peak heavy oilfield and priddis high-resolution near-surface surveys.