Coastal wetlands as recorders of earthquake subsidence in the Aegean: a case study of the 1894 Gulf of Atalanti earthquakes, central Greece

Cundy, A.B., Kortekaas, S., Dewez, T., Stewart, I.S., Collins, P.E.F., Croudace, I.W., Maroukian, H., Papanastassiou, D., Gaki-Papanastassiou, P., Pavlopoulos, K. and Dawson, A. (2000) Coastal wetlands as recorders of earthquake subsidence in the Aegean: a case study of the 1894 Gulf of Atalanti earthquakes, central Greece. Marine Geology, 170 (1-2), 3-26. (doi:10.1016/S0025-3227(00)00062-1).

Abstract

Earthquakes may have a major impact on the morphology and evolution of coasts in tectonically active areas. In the area of the Gulf of Atalanti, central Greece, a damaging earthquake sequence in 1894 is reported to have caused nearshore slumping, tsunami-induced flooding, and decimetre-to metre-scale coastal subsidence. The earthquakes caused major changes to coastal configuration, in particular the separation of the Gaïduronisi peninsula from the mainland.

Detailed stratigraphical, microfossil and radiometric (210Pb and 137Cs) analyses of coastal wetlands around the Gulf of Atalanti show that these environments preserve evidence of sudden, lasting subsidence contemporaneous with the 1894 events, with foraminiferal assemblages at a site on the mainland opposite the island indicating an abrupt change from supratidal soil to intertidal marine conditions. The elevation change indicated by this terrestrial to marine transition is 30–80 cm. The coastal stratigraphy in the Atalanti area however lacks laterally extensive sharp soil–mud contacts or tsunami deposits of the type used in identifying past earthquake subsidence events at plate–boundary settings. Despite the major earthquake-induced changes in coastal configuration, the stratigraphical signature of the 1894 earthquakes is relatively subtle, and is consequently difficult to distinguish from other rapid coastal changes (e.g. storm events or barrier breaching) without high-resolution dating control and reference to documentary records. For this reason, coastal wetland stratigraphies are only likely to be useful in identifying pre-historical or poorly documented earthquakes in the Aegean at sites where metre-scale coseismic elevation changes and/or major tsunami inundation have occurred. In addition, the resolution of the biostratigraphic data reported here is insufficient to distinguish between the contrasting fault rupture models for the 1894 events. The coastal elevation changes recorded in these wetlands, however, are best accounted for by a slip of 1 m on a multi-segment fault.

This record has no associated files available for download.

Contributors

Author: A.B. Cundy

Download statistics