Wide-angle seismic data reveal extensive overpressures in the Eastern Black Sea Basin

We present new data that explores the link between pore pressure and seismic velocity to
estimate the magnitude of the overpressure within the deep sediments of the Eastern Black
Sea basin. New wide-angle seismic data, combined with coincident reflection data, have
been modelled simultaneously using the seismic tomography code, Jive3D, to provide a wellconstrained
seismic velocity model of the sediments. Our models reveal a widespread lowvelocity
zone at the depth of 5.5–8.5 km, which is characterized by a velocity decrease from
3.5 to ∼2.5 km s−1. Using two separate methods that relate changes in seismic velocity to
changes in effective stress, we estimate pore pressures of at least 160 MPa within the lowvelocity
zone. These pore pressures give λ values of 0.8–0.9 within the centre of the basin and
above the Mid-Black Sea High. The low-velocity zone occurs within the Maikop formation,
an organic-rich mud layer identified as the source of mud volcanism in the Black Sea and
South Caspian Sea.