Active Tectonic Framework and Seismic Stratigraphy of the Central Aegean: The Chios-Ikaria-Samos Marine Area

The marine area between Chios, Ikaria and Samos islands occupies a key position within the Central Aegean extensional domain, encompassing the offshore segments of several active fault systems, including those responsible for the 30 October 2020 Mw 7.0 Samos earthquake. Despite the significant seismic and tsunami hazards, the subsurface stratigraphic architecture and three-dimensional geometry of active faults in this region are remain poorly constrained. The aim of this study is to present preliminary results of an integrated seismic stratigraphic and structural interpretation based on five multichannel seismic reflection profiles (total length ~364 km) obtained by MTA and reprocessed into SEG-Y format. The study also includes previously published seismic profiles reinterpreted within a tectonostratigraphic framework, as well as high-resolution bathymetric data compiled from SHOD and international sources.

The seismic profiles indicate the presence of a prominent acoustic basement, overlain by a thick Neogene-Quaternary sedimentary succession, characterised by laterally continuous to locally progradational reflector packages. The basement surface exhibits significant relief, featuring a complex network of high-angle normal faults that form a system of asymmetric basins and structural highs. Above the basement, the sedimentary architecture displays a variety of reflector geometries, including parallel, divergent and clinoform patterns. These patterns are indicative of deltaic or slope-related depositional architectures, particularly in the western part of the study area.

Both newly processed and literature seismic sections demonstrate a predominant orientation of NW-SE and NE-SW-striking faults, which is consistent with the present-day Aegean extensional regime. Several of these faults clearly intersect with the shallowest reflectors, thereby indicating Quaternary to potentially present-day activity. The North Ikaria Basin, in particular, exhibits notable fault-controlled subsidence, expressed by thickened sedimentary packages and cumulative vertical displacements. These observations suggest the presence of long-lived tectonic control on basin development.

The three-dimensional correlation of fault planes and key stratigraphic reflectors enables the characterization of the geometry of the basin-bounding structures, and the evaluation of their possible kinematic linkage with the onshore fault systems of western Anatolia and the eastern Aegean islands. The integrated interpretation highlights the role of segmented normal fault systems in controlling basin architecture, sediment distribution patterns and accommodation space during the Neogene-Quaternary evolution of the Central Aegean back-arc domain.

These results provide a first-order seismic stratigraphic and structural framework for the offshore region between Chios, Ikaria and Samos. This framework is the result of the combination of newly reprocessed and legacy seismic datasets, which have been evaluated within a consistent tectonic context. The ongoing analysis will form the basis for detailed fault mapping, thickness distribution and kinematic reconstructions, and will contribute to a better understanding of the relationship between active crustal deformation and seismic hazard in the eastern Aegean region.