Original paper

Holocene tsunamigenic sediments and tsunami modelling in the Thermaikos Gulf area (northern Greece)

Reicherter, Klaus; Papanikolaou, Ioannis; Roger, Jean; Mathes-Schmidt, Margret; Papanikolaou, Dimitrios; Rössler, Stefan; Grützner, Christoph; Stamatis, Georgios

Abstract

Shallow drill cores in flat and southerly exposed coastal areas around the Thermaikos Gulf (Thessaloniki, northern Greece) provided evidence for past high energy sedimentary events, which are interpreted as tsunamites. A tsunamigenic source is located along the western tip of the North Anatolian Fault Zone (NAFZ) in the North Aegean Basin, where water depths ranging between 1.200 and 1.650 m are sufficiently deep to generate tsunamis. However, the event layers up to now cannot be assigned to individual seismic or landslide sources, but the potential of a tsunami threat in the Thermaikos Gulf area can now be tested, following both sedimentological and modelling processes. Such potential threat regarding the Thermaikos Gulf has only recently been notified, but never tested and studied in depth.As a result, several Holocene coarse clastic marine layers have been found intercalated in clayey or gypsiferous lagoonal deposits. These layers have erosive bases, show fining-up and thinning-up sequences, and include shell debris, foraminifera and rip-up clasts of lagoonal sediments. A widely observed significant feature of these layers involves mud-coated beach clasts, clasts that rework the high-plasticity clays of lagoons. Such features that indicate highly disturbed sedimentological processes (hyperpycnal flows) are rarely described elsewhere. Multiple intercalations of these layers with all the mentioned indicative features downhole are interpreted as paleotsunami deposits from tsunamis generated by earthquakes or earthquake-triggered submarine landslides in the Thermaikos Gulf.Modelling of the tsunami potential of the basin-bounding fault southwards of the Thermaikos Gulf provides an example for possible tsunami generation at only one segment of NAFZ along an approx. 55 km normal fault at the southern fault-bound margin of the North Aegean Basin.

Keywords

aegean seatsunamitestsunami modellinggreecethermaikos gulf