The two choragic columns on the South Slope of the Acropolis as witnesses of the seismic history of the center of Athens
The object of this study is to make a detailed survey and architectural documentation of two choragic columns on the south slope of the Acropolis, above the Monument of Thrasyllos. The study contributes to research on the seismic past of central Athens, incorporating evidence from the seismic load the columns bear.
This documentation was done by placing light metallic scaffolding on the two columns. Significant measurements were made on the spot and all details, in terms of both their present condition and their graphic restoration, were recorded.
The morphological features of the two columns, including the elegant profiles of their bases, the slight convexity (entasis) of their shafts, the brilliant design of their unique Corinthian capitals and their construction features, such as the high degree of precision and fine surface treatment of their stepped platforms and shafts, the use of Classical double T-shaped clamps, and elevating techniques led to the conclusion that the two columns were built in the late Classical or early Hellenistic period and constitute exceptional works of ancient Greek art.
One significant finding of the study, which is very rare on the Acropolis monuments, is the preservation of a large part of the original polychromy of the columns. On the eastern capital the initial cyan blue background of the floral decoration has been preserved to a large extent, while traces of red can be seen in many places on both columns.
By recording the damages to the columns and the systematic diagnosis of their causes it was deduced that the two choragic monuments had suffered at least one powerful seismic shock in the distant past, which caused them significant deformation. The patina on the fracture surface and the traces of erosion allowed us to conclude that this earthquake, which has not been recorded in the historical sources, should be dated approximately to the Middle Ages. It must have been much more severe than the earthquakes that struck Athens in 1981 and 1999, in which lives were lost and significant damages were inflicted on the cityβ€™s buildings and on the Acropolis monuments, while leaving these two choragic columns largely unharmed.
The seismic behaviour of the two columns was also tested computationally by a dynamic non-linear analysis of their models using the Finite Elements method on the 1999 Parnitha earthquake and with data obtained from the instrumental measurements of their features by the Seismology Laboratory at the National and Kapodistrian University of Athens.
Final report (in Greek)
Costas Zambas, PhD, Civil Engineer, National Technical University of Athens
Nicolas Ambraseys, Academician, Professor of Engineering Seismology
Constantinos Boletis, MSc, Architect, Restorer
Ifigeneia Zampa, MSc, Geologist