Characterization of selected station sites of the Hellenic Accelerometer Network (HAN)

Abstact In this study site characterization of twelve accelerometer station sites of the Hellenic Accelerometers Network (HAN) is presented. An established European protocol is applied that consists of non-invasive active (Multichannel Analysis of Surface Waves: MASW) and passive (Ambient Vibration Analysis: AVA) methods. Data processing is carried out systematically, using new techniques of dispersion curves estimation and their inversion to obtain 1D shear wave velocity profiles at the examined sites. Surface geology and other site information previously indicated six sites as reference “rock” and six as stiff to soft soil. After data processing in this study, it was determined that only five of them fulfil the engineering bedrock criterion (\(\:{V}S30\) > 800 m/s), with one of them - station ART2 (Arta) - identified as very hard rock (\(\:{V}S30\) ~2000 m/s). The remaining seven investigated sites fall within stiff to soft soil categories (380 ≤ \(\:{V}S30\) ≤ 618 m/s). The results show that, for stiff soil and rock sites, geology and topographic slope- inferred \(\:{V}S30\) values, in some cases significantly, especially for \(\:{V}S30\) > 500 m/s. These results highlight the importance of direct geophysical investigation for reliable site classification and for reducing bias in ground motion modeling, e.g. Ground-Motion Models (GMMs) and Generalized Inversion Techniques (GITs). The updated station sites characterization metadata set provides a reference framework for future updates of the Hellenic Accelerometers Network recordings and contributes to the harmonization of European strong-motion stations metadata within EPOS as well as in the European Strong Motion database.