Synthesizing signal from noise recordings along the ocean bottom

Direct acoustic waves extracted from ocean-bottom ambient noise.

Using the passive portion of the continuous recordings from a North Sea data set, I characterize the marine ambient noise field and perform ambient noise cross-correlations on multicomponent ocean-bottom node data. Spectrograms, plots of spectral power as a function of distance from the operating platform, and beamforming suggest that the platform dominates the noise field for frequencies up to 40 Hz (particularly in the vertical geophones). As Love waves often have higher signal-to-noise ratios than corresponding Scholte waves, I apply the ambient noise cross-correlation method to multicomponent ocean-bottom node recordings in hopes of recovering platform-generated wave modes. For frequencies between 5 and 10 Hz, Love-wave energy appears to be just as coherent as Scholte-wave energy. For frequencies between 40 and 80 Hz, there are signs of an acoustic wave traveling on the hydrophone and vertical geophone components. The presence of these acoustic waves is promising for future work in passive fathometry.

Data courtesy of Apache North Sea Limited.

Conference Abstracts
Society of Exploration Geophysicists 2016 [abstract]