Peak and integral seismic parameters of L’Aquila 2009 ground motions: observed vs code provision values

Abstract. The M w 6.3 L’Aquila earthquake of April 6, 2009 hit a wide area of the Abruzzo region (Central Italy). The epicentre of the main shock was very close to the urban centre of L’Aquila, the regional capital, with an epicentral distance less than 10 km. It was the strongest earthquake ever recorded in Italy which has provided ground motion recordings from accelerometric stations located in close proximity to the epicentre. Because of this, several remarkable results can be achieved by analysing the strong motion recorded signals in terms of peak (PGA, PGV and PGD) and integral (Housner Intensity, I H ) seismic parameters. Additionally, an alternative time-domain representation of recorded signals has been used to furnish a rapid comparison of traces recorded at different stations and along different directions. Some comparisons between the response spectra derived from the recordings and the elastic demand spectra provided in the new seismic Italian code have also been performed. PGA recorded values are very high and generally higher than code values for seismic actions with return period T R = 475 years. In some cases, this also happens for seismic actions with T R up to 2,475 years. With regard to I H , recorded values are generally higher for T R = 475 years, whilst they are remarkably lower for T R = 2,475 years. Accurate analyses have been carried out in the article to better understand the above differences and their significance and implications.