Walking in the Null Space of Monochannel Boomer Data Inversion

Monochannel Boomer surveys can image shallow marine sediments in ecologically sensitive areas such as lagoons or in heavily trafficked areas such as harbors, where shipping restrictions impede long streamers. However, the advantage of low cost comes at the cost of a loss of information. Multi-channel systems use different offsets to estimate velocity, thickness and even density (by AVO) of shallow marine sediments. These rock properties are important for offshore engineering and marine geology. In this paper, we show that by inverting the traveltime and amplitude of multiples and primaries, we obtain comparable information. Tomographic inversion suffers from ambiguity when the available data cannot constrain the chosen Earth model parameters, and multiple solutions fit the experimental data equally well. In jargoon, there is a Null Space in the solution space in which we can “walk”: we can select there an arbitrary solution that ideally satisfies another criterion, such as geologic constraints or reduction of model complexity. Boomer profiles are characterized by two features: firstly, the high spatial resolution, and secondly, the smooth lateral changes of the shallow sediments. These reasons argue for the introduction of smoothing conditions to reduce the inversion ambiguity.