Near field domain effects and their consideration in the international and Italian seismic codes

It is widely proven that in the field area near a seismic source the characteristics of the seismic ground motion (near field) could be meaningfully different from those far from the source (far field), not only in terms of intensity but also in terms of nature and typology. Nevertheless, structures are usually designed on the base of accelerations derived from ordinary probabilistic seismic hazard analyses (PSHA) under the hypothesis of far-field conditions, and further modified taking into account the local seismic response. As a consequence, a structure might not have proper safety levels if it is located close to an earthquake source (i.e., in a potential near-field domain). The purpose of this paper is to analyse the near-field effects on the seismic hazard, focusing in particular on the Italian case. For this aim, an essential bibliographic overview is presented, showing the specific seismic effects in the proximity of an earthquake source and the related consequences on the structures. Furthermore, the paper presents a brief analysis on how some international seismic building codes consider the near-field effects, underlining the fact that, nowadays, the near field effects are not considered in the Italian codes. For this reason, the authors suggest to consider the increase of the seismic demand in the potential near-field domains, introducing the concept of "potential epicentral area contribution to hazard - PEACH", directly associated to the specific characteristics of the seismogenic source. Finally, the limits of the proposed approach and the prospective of its application in Italy are outlined. © 2014 - OGS.