Impact of Local Site Conditions on the Seismic Response of the Athenian Acropolis Hill

In the literature, records and analyses have shown that in earthquake-prone areas local site conditions tend to alter the strong motion at the ground surface. More specifically, the surface topography, in combination to the soil stratigraphy and/or the geomorphology of the seismic bedrock, may have a substantial impact on the amplitude, the frequency content, and/or the duration of the seismic motion at the ground surface. The current study is involved with the Athenian Acropolis Hill, which is an unusual case of local site conditions affecting ground motion as a rock outcrop of limestone overlies the relatively soft Athenian schist. Since monuments of paramount importance are founded on the Hill (i.e. Parthenon, Propylaea, Erechtheion and Temple of Athena Nike) and Athens is characterised by moderate to high seismicity, a seismic array of accelerographs has been installed by the National Observatory of Athens and the Acropolis Restoration Service at specific locations on the Hill in order to monitor its seismic response in real time. Aiming to assess the impact of local site conditions on the seismic response of the Hill, an evaluation of the available recorded acceleration time histories has been conducted. Additionally, two-dimensional numerical simulations have been performed utilising the finite-element method. Various excitations, such as simple pulses and records obtained by the seismic array, have been used as input motion for the numerical analyses. Despite the discrepancies, the numerical results are in good agreement with the available records and demonstrate the importance of local site conditions on the seismic response of the Acropolis Hill.