Preliminary Results of Site Effects Assessment in Mtskheta (Georgia)

Seismic hazard and risk assessment is a crucial issue for Georgia, a country located in the Caucasus, which is one of the most seismically active regions in Alpine-Himalayan collision belt. It has long been known that subsoil conditions may have a significant influence on the expression of earthquake motions at the surface, modifying both amplitude as well as the frequency content and duration of the seismic ground motion. In this regard, seismic microzonation studies aimed at identifying and mapping zones, in a given area, characterized by homogeneous seismic behavior, represent a worldwide-accepted tool for the mitigation of seismic risk. In this paper, we provide the preliminary results of the first site effects assessment performed in the urban area of Mtskheta (Georgia). Our main outcomes consist in: (i) a geological map focused on the study area; (ii) a distribution map of resonance frequencies (f0 and f1); (iii) an estimation of the average shearwave velocity of the upper 30 m (VS,30) and (iv) the amplification factors fromstandard acceleration response spectra according to the EC8 classification. The results obtained will represent a first step toward reducing seismic risk in Georgia and providing a knowledge base of local seismic hazard, useful for effective seismic risk mitigation strategies