Spread tsunami impact in East Tunisia contemporaneous of the CE 365 Crete earthquake

Abstract

<p>New field investigations along the East Tunisian coastline reveal sedimentary deposits and damaged localities that may account for a catastrophic event during late Holocene. North of Sfax - Thyna city (at Henchir El Majdoul site) ~3.4 m high cliff coastal marine and alluvial terraces show a 20 to 50-cm-thick chaotic layer with sandy coarse gravels mixed with limestone beach-rocks, reworked blocks, broken shells of marine and lagoon gastropods and lamellibranch mollusks, organic matter, and Roman pottery. The chaotic layer truncates a succession of sandy-silty paleosol, covers Roman settlements and is overlain by fire remains and a relatively thin (~10 cm) sandy-silty aeolian unit and ~1-m-thick alluvial deposits. Charcoal samples collected at 10 cm below and 4 cm above the catastrophic deposits provide radiocarbon dating that brackets a catastrophic event between 286 and 370 CE (2s). Beside the damaged Roman site of Thyna, other localities of the east Tunisian coastline such as Neapolis (Nabeul) near Tunis, Hadrumete (Sousse), Meninx-town in Girba (Djerba), Wadi Ennouili (Gulf of Gabes), and Sabratha (in Libya) experienced major damage and abandonment of sites in Fifth century. The extent of damage from northern Libya to northern Tunisia at the Fourth century and radiocarbon dating, added to the 2.6 m thick turbidite deposits west of Malta correlate with the major tsunamigenic earthquake of 21 July 365 (Mw ~ 8) in west Crete (Greece). Numerical modelling of the tsunami caused by an earthquake in the Hellenic Arc subduction zone suggests more than 3.5 m high tsunami waves propagation affecting the Tunisia coastline, resulting in a run-up consistent with the stratigraphic evidence presented here. The catastrophic deposits, offshore-onshore correlations, archeological damage and modelling of tsunami waves suggest a new, higher-resolution, assessment of the tsunami hazard leading to a better estimate of tsunami risk on the eastern coast of Tunisia.</p>