Abstract. We present a high-resolution P-wave velocity model of the sedimentary cover
and the uppermost basement to ∼3 km depth obtained by
full-waveform inversion of multichannel seismic data acquired with a
6 km long streamer in the Alboran Sea (SE Iberia). The inherent
non-linearity of the method, especially for short-offset, band-limited
seismic data as this one, is circumvented by applying a data processing or modelling sequence consisting of three steps: (1) data
re-datuming by back-propagation of the recorded seismograms to the
seafloor; (2) joint refraction and reflection travel-time tomography
combining the original and the re-datumed shot gathers; and (3) full-waveform inversion of the
original shot gathers using the model obtained by travel-time tomography as
initial reference. The final velocity model shows a number of geological structures that
cannot be identified in the travel-time tomography models or easily
interpreted from seismic reflection images alone. A sharp strong velocity
contrast accurately defines the geometry of the top of the basement.
Several low-velocity zones that may correspond to the abrupt velocity
change across steeply dipping normal faults are observed at the flanks of
the basin. A 200–300 m thick, high-velocity layer embedded within
lower-velocity sediment may correspond to evaporites deposited during the
Messinian crisis. The results confirm that the combination of data
re-datuming and joint refraction and reflection travel-time inversion
provides reference models that are accurate enough to apply full-waveform inversion to
relatively short offset streamer data in deep-water settings starting at
a field-data standard low-frequency content of 6 Hz.