Fast method to transform chirp envelope data into pseudo-seismic data

Chirp technology is an acoustic tool for imaging the shallow seabed with a high resolution, used for investigations of modern to Quaternary sedimentary structures and processes and more applied goals, such as hazard surveys for drilling, archeology, geology or engineering fields. In this paper, we present new methods that improve such imaging. During the standard acquisition, the Chirp waveforms are converted into analytic signals and only their envelope is preserved and interpreted, because the highly oscillating signal is otherwise difficult to be identified visually. Doing so, however, the phase information is lost, and the final processing is limited mainly to simple time-varying gain recovery or filtering. We present a work flow including a derivative step to transform the enveloped signal into a seismic-like waveform. In this way, we can apply processing tools as FX deconvolution and migration to improve the signal/noise ratio and reduce diffractions. This method allows reviving standard and legacy Chirp data where the full-waveform information is missing.