Converted PS-wave Velocity Structure from Full Waveform Inversion Reveal High Pore Pressures in the Eastern Black Sea

We model an approximately 100 km southeast-northwest transect in the eastern part of the EBSB, where 15 ocean bottom seismometers were placed between the coast and the centre of the basin. The data are of excellent quality and we were able to analyse both previously indentified P-wave reflectors and some new reflectors found during the processing of this model.Previous analysis has revealed the presence of a widespread low-velocity zone within the basin fill, which coincides with the Maikop formation, an important sedimentary sequence of this region due to its potential as a hydrocarbon source. This low-velocity zone is interpreted as due to excess pore pressures. Our detailed S wave model extends to 3.5 km below the seabed, with a single layer beneath this depth that extends to a deeper horizon marking the base of post-rift sediments. The Poisson’s ratio varies from approximately 0.49 close to the seabed to ~0.38 in one of the deepest layers . In the low velocity zone there is an increase of the Poisson’s ratio. We then use full-waveform inversion to resolve finer structure and estimate pore pressures using Kuster-Toksoz theory and Differential Effective Medium theory.