1D Site characterization of National Accelerometer stations in Greece based on earthquake recordings and the Diffuse Filed Concept (DFCe)

This study presents the site characterization of 133 selected stations in the National Accelerometer Network of Greece. All available earthquake recordings for various distances, magnitudes and azimuths around the station are compiled and processed to estimate a stable and reliable average Horizontal -to-Vertical Spectral Ratio (eHVSR). The earthquake records used have magnitude range 4 ≤ M < 6, with focal depth ranging from 0 to 40km and hypocentral distances 12 km ≤ R_hyp ≤ 300 km. Using the Diffuse Filed Concept for earthquakes (DFCe), and incorporating limited a priori geological information, available for the area around the station, the estimated eHVSRs were utilized in an inversion framework to estimate the best misfit velocity profiles down to seismological bedrock (where Vs>=3km/sec). Comparisons of these estimated velocity profiles with existing ones for the selected stations based on other geophysical or/and geotechnical methods, revealed good agreement, encouraging broader application of this methodology for the rest of stations.

In accordance with recommendations from the SERA project, seven key indicators were calculated for each of the 133 stations and are presented as follows: (1) Resonance frequency (f₀), (2) Shear wave velocity of the uppermost 30 meters (Vs₃₀), (3) Surface geology description, (4) Current EC8 site class, (5) Depth of the seismological bedrock (H_3km/s), (6) Depth of the engineering bedrock (H_0.8km/s) and (7) V_SZ full profiles where available. Such comprehensive site characterization of accelerometer stations enhances regional and international strong-motion databases (e.g. ESM db) and contributes to exploiting earthquake recordings to their full potential for engineering and seismological applications.