Neogene stratigraphic architecture and three-dimensional velocity structure beneath the Gulf of İzmir (western Anatolia) from reflection traveltime tomography

There are basins with proven hydrocarbon and geothermal sources across western Anatolia. Only a few moderate-scale tomography studies investigate their velocity structure and stratigraphical architecture. We present the first 3-D Neogene velocity-depth model of the Gulf of İzmir down to ∼1.7 km. The aim is displaying a better portrait of the 3-D stratigraphical architecture, velocity structure of the Gulf of İzmir, and constitute a solid foundation for future studies. We provide the first 3-D view of the complex Late-Miocene basement topography representing an unconformity surface. It consists of basins and ridges separating the Miocene basement (SSU3) and overlying Plio-Quaternary deposits (SSU2 and SSU1). Four N[sbnd]S oriented volcanic ridges accommodate offshore Uzun Island, Karaburun, and Foça. They border a basin with a thickness of ∼720 m in the mid-central and a deeper one with ∼1400 m in the northernmost sector of the gulf. The 3-D P-wave traveltime tomography results indicate prominent lateral and vertical velocity variations at different depths (∼300–800 m). The low-velocity zones (1600 ≤ Vp ≤ 1850 m/s) are interrupted laterally by the high-velocity zones (2150 ≤ Vp ≤ 2350 m/s) that corresponds to the squeezed sediments within Plio-Quaternary basins deformed by the N[sbnd]S trending strike-slip faults of Karaburun Fault Zone. The same faults also deform the volcanic basement highs identified by the high velocities (>2600 m/s). The thick depocenter with low-velocity anomalies in the outer gulf suggests the gas/fluid containing sediments. Their controlling faults are likely responsible for the circulation of gas/fluid and heat transfer from a deeper source making the region target for exploration activities.