THE MAIN SEQUENCE OF SEISMIC MICRO ZONING

Experience in the field of seismic protectionshows that the main concept of seismic protection inUkraine should be the introduction of seismic designand construction of residential and industrial facilitiesbased on objective knowledge of the quantitativeparameters of the actual seismic hazard in the areawhere specific construction sites are located. Allpublic authorities and business entities within thecountry must ensure seismic protection of structures,facilities and areas from future earthquakes withintheir competence.The level of seismic hazard is an objectivecharacteristic of the territory and is determined bya set of works such as: general seismic zoning ofthe country's territory, detailed seismic zoning ofits individual areas, seismic microzoning of areas.The most dangerous for buildings and structuresare seismic vibrations occurring in the horizontalplane. Taking into account the subducted locationof the main seismic source of the Vrancea zone,the approach of seismic vibrations to the bottomsurface is almost vertical. The main contribution tothe horizontal vibrations on the daytime surface ismade by transverse waves. In this regard, estimatesof seismicity increase based on seismic velocities oftransverse waves will be the most representative.The complex of works on seismic microzoningis carried out to assess seismic hazard, which takesinto account the influence of local soil conditionson the intensity of seismic vibrations on the surfaceof the construction (operational) site. The influenceof groundwater level, peculiarities of the sitemorphology and its location, as well as possibleoccurrence of dangerous resonance phenomena onthe site are also taken into account. The result ofseismic microzoning is a construction and assemblymap of the investigated site and sets of calculatedaccelerograms for the reference point or for each ofthe engineering and geological sites identified on thesite.