f Air gun signatures and the minimum-phase assumption

The air-gun array signature is close to minimum-phase as a function of continuous time, in the sense that for processing purposes its phase spectrum can be derived from the Hilbert transform of the logarithm of its amplitude spectrum . This phase spectrum is different, however, from the minimum-phase spectrum that is estimated by spiking deconvolution for a sampled and time-windowed version of the signature . As a consequence there are large phase errors when spiking deconvolution is applied to an airgun array signature or to a recording instrument response .