Seismic microzonation regulations of the Emilia-Romagna region (Italy).

We describe a proposal of seismic microzonation regulations for the Emilia-Romagna Region to be eventually adopted as a regional code for land use planning. These regulations supply the reference input motion for each municipality and define three levels of analysis to be selected on the base of the seismicity level and the economical relevancy of the area under investigation. The prescribed microzonation studies are organized into three levels. The first level, which could be thought of as preliminary zonation, is based on the available geological and geotechnical information and does not require further additional field investigations. The second level mainly focuses on the seismic site amplification assessment and requires additional geotechnical and geophysical investigations. This level supplies tables which relates ground motion amplification to average Vs and bedrock depth of the site. Site effects are expressed in terms of expected PGA and Housner Intensity; the latter is computed by assuming two intervals of integration. The third level is recommended in cases where instability phenomena cannot be excluded or major or strategic buildings and lifelines must be located.