Seismic coastal uplift and subsidence in Rhodes Island, Aegean Arc: Evidence from an uplifted ancient harbour

摘要

Archaeological evidence from a 2400 years old harbour, currently about 3 m above sea-level, sheds light on an enigmatic sequence of coastal uplift and subsidence along the coasts of Rhodes Island, close to a N4 km deep trough marking the east edge of the Aegean Arc. The tectonics of this area are not clear, because of the absence of major earthquakes in the last 80 years, but are likely to be controlled by a combination of shear and compression producing strong earthquakes, some associated with tsunamis and some with thrust-uplifted notches. The latter, up to 6000 years old, also show evidence of phases of subsidence. Our study focuses on remains of shipsheds, in particular a ramp used to pull warships out of the water and keep them protected under cover duringwinter. This ramp was constructed between approximately 250-225 BC and somedecades later itwas repaved, after amajor earthquake destroyed the townof Rhodes andmost probably the harbour and sheltered ships, as historical evidence reveals. 300 years later the harbour was to a great part abandoned because of a coastal uplift. The only reasonable explanation for the ramp reconstructionwas to counteract a 1 m seismic subsidence at around 220 BC or earlier. Several possible explanations can be proposed for the earthquakewhich produced seismic subsidence alternatingwith uplift in Rhodes, in a pattern of vertical motions different from that observed in Crete, or other convergent boundaries.