Estimation of Vertical Amplification Correction Function (VACF) in Greece Based on the Generalized Inversion Technique of Strong Motion and Diffuse Field Concept on Earthquakes

ABSTRACT The main purpose of this study is the estimation of site amplification factors (SAFs) of the horizontal component of the ground motion to improve seismic hazard assessment because these factors play an important role in seismic site response. Toward this effort, the subsurface structure and the related amplification effects of two accelerometer stations in Greece were acquired, examining their use as reference stations. This was achieved by computing the vertical-to-horizontal spectral ratio corresponding to the depth of the seismological bedrock and comparing it with the theoretical value of ∼0.76 for seismological reference stations, according to the diffuse field concept for earthquakes, in the case of a Poisson solid. Thereafter, the two selected reference stations were used to invert for horizontal and vertical SAFs for a total of 151 accelerometer stations in Greece. The vertical SAFs for each site were used to estimate a mean representative vertical amplification correction functions (VACFs) in Greece. These VACFs can be used for assessing horizontal SAFs based on the horizontal-to-vertical ratio of earthquake, where it is available, contributing thus to site-specific seismic hazard assessment in regions where there is a lack of observed classical amplification spectral ratios with an adjacent surface or borehole reference site. Simulated horizontal SAFs were calculated for sites out of the examined dataset for the frequency range 0.3–15 Hz, to evaluate the effectiveness of the proposed VACFs.