Site response analyses for seismic microzonation: Case-histories, results and applications in Central Italy

The paper presents the main results of 1D/2D site response numerical analyses at 4 sites selected among the 137 municipalities of the Seismic Microzonation study which has been carried out after the 2016 Central Italy seismic sequence. Complex site effects at ridge/slope crest and at the edge of slope covers lead to 2D aggravation factors in the range 2-3 with respect to ground motion predicted with simple 1D analyses. A systematic comparison carried out for all 137 municipalities, between computed and Italian code NTC18 amplification factors highlighted that the code is generally conservative at low-to-medium periods and overconservative at medium-to-high periods. A strategy for the use of microzonation site response analyses in support of seismic design for the reconstruction process is finally suggested.