iSIMM Experience with Peak- and Bubble-Tuned Sources for Generating Low Frequencies

The iSIMM project has demonstrated the effectiveness of low-frequency acquisition in countering the loss due to scattering by the high-impedance contrasts and rough surfaces presented by stacked basalt flows (Spitzer et al., 2005). Both the ocean-bottom seismometer (OBS) profiles and the densely sampled towed-streamer profiles in the iSIMM surveys allowed comparison of deep-towed, peak-tuned, and bubble-tuned airgun sources. Supported by earlier analysis (Lunnon et al., 2003), we find source tow depth has greater impact upon bandwidth than does tuning mode, although, for the configurations tested, the bubble-tuned source produced a more compact signature. Shot-by-shot signature deconvolution was successfully applied to bubble-tuned streamer data in sub-critical regimes, but wide-angle signatures were adversely affected by standard deconvolution. This paper evaluates the performance of the peak- and bubble-tuned sources and presents a robust shaping deconvolution.