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Aegeus Society For Aegean Prehistory

ARTICLES | 2011

19 September 2011

Modelling of tsunami generated by the giant Late Bronze Age eruption of Thera, South Aegean Sea, Greece

T. Novikova, G.A. Papadopoulos & F.W. McCoy Geophysical Journal International 186 (2011): 665–680.

Abstract

Tsunami generated by the Late Bronze Age (LBA) eruption of Thera were simulated using synthetic tide records produced for selected nearshore (∼20 m depths) sites of northern Crete, the Cyclades Islands, SW Turkey and Sicily. Inundation distances inland were also calculated along northern Crete. Modelling was performed by incorporating fully non-linear Boussinesq wave theory with two tsunamigenic mechanisms. The first involved the entry of pyroclastic flows into the sea, assuming a thick (55 m; 30 km3) flow entering the sea along the south coast of Thera in three different directions all directed towards northern Crete, then a thin pyroclastic flow (1m; 1.2 km3) entering the sea along the north coast of Thera directed towards the Cyclades Islands. Flows were modelled as a solid block that slowly decelerates along a horizontal surface. The second mechanism assumed caldera collapse, of 19 km3 and 34 km3 modelled as a dynamic landslide producing rapid vertical displacements. Calculated nearshore wave amplitudes varied from a few metres to 28malong northern Crete from pyroclastic flows, and up to 19 m from caldera collapse (34 km3 volume). Inundation distances on Crete were 250–450 m.Waves produced by pyroclastic flows were highly focused, however, as a function of sea entry direction. Smaller volume pyroclastic flows produced nearshore wave amplitudes up to 4 m in the Cyclades islands north of Thera. Wave amplitudes in the Cyclades from smaller volume caldera collapse (19 km3) were up to 24 m, whereas in SW Turkey were as low as 2.1 and 0.8 m (Didim and Fethye where LBA tsunami deposits have been found). Wave amplitudes for the larger volume caldera collapse (34 km3) were generally 2.5–3 times larger than those generated by the smaller volume collapse (19 km3). These results provide estimates for understanding possible consequences of tsunami impact in LBA coastal zones, thus providing criteria at archaeological sites for detecting inundation damage, as well as for contemporary hazard assessment; they also provide additional criteria for deciphering homogenite layers in the abyssal stratigraphy of the Ionian and eastern Mediterranean Seas.

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