Seismic hazard assessment for the Tbilisi test area (eastern Georgia)

The seismic hazard of eastern Georgia has been computed with the seismotectonic probabilism approach. A logic tree was used to take into account the different hypotheses on the seismogenesis of the Caucasus region, and to model seismicity and attenuation. In addition to the usual maps referring to different types of terrains (rock, stiff, and soft soil), the soil hazard map for the Tbilisi broader area has been computed by aggregating the results according to the specific characteristics of the terrains. Ground motions between 0.16 and 0.32 g are expected in accordance with the soil conditions in Tbilisi town, while values between 0.32 and 0.40 are expected towards the Caucasus ridge. The uniform hazard response spectrum for Tbilisi for rock and stiff soil is almost flat for periods lower than 0.3 s. This decreases for higher periods, while the decrease is less evident for soft soil and the spectrum remains high for periods lower than 0.5 s.