Seismic risk mitigation at Campi Flegrei in volcanic unrest

Abstract

Campi Flegrei is a densely populated volcanic area in Italy. Its inner caldera periodically experiences uplift and subsidence, known as bradyseism, also accompanied by seismic activity. In the last decade, with uplift rates up to 2 cm/month, about nine-thousand earthquakes were recorded. Upon request of the local administration, the most updated data were collected and analyzed to evaluate the risk management strategy consisting of structural retrofitting according to the building code. Here it is shown that the reference moment magnitude is in the range \(\left({{\mathrm{4.4,5.1}}}\right)\), based on fault mapping, geomorphological inference, earthquake relocation, stress-drop analysis, and ground motion modelling. Earthquake forecasting enabled computing the exceedance probabilities of these magnitudes. Earthquake engineering showed that the minimum magnitudes expected to cause exceedance of design ground motion, are larger than the reference magnitudes. Finally, the risk reduction implied by the safety levels of new constructions was assessed for reinforced concrete buildings.