Italian strong motion records in ITACA: overview and record processing

The published version 1.0 of the new Italian strong-motion database ITACA (Italian ACcelerometric Archive,http://itaca.mi.ingv.it) includes to date (December 2010) about 4,000 three-component waveforms up to M 6.9,from more than 1,800 earthquakes up to 6.9,recorded by about 400 stations in the period 1972–2009. The uncorrected and corrected strong motion data are archived and can be retrieved with their metadata,concerning events,stations and waveforms. The aim of this paper is to present the procedures for processing the records included in ITACA,accounting for the heterogeneity of this data set,both in terms of quality and amplitude of records as well as illustrating the main features of the ITACA strong-motion dataset. Later,we focus on the “exceptional” ground-motion records,that we,conventionally,denote as those having peak acceleration and peak velocity larger than 300 cm/s2 and 15 cm/s,respectively. These records are less than 2% of the whole ITACA dataset but they are the most relevant for the seismic hazard and engineering implications. Such large peak values,recorded at distances up to 30 km,are related not only to the strongest Italian earthquakes,but also to events with magnitude down to 4. Furthermore,we investigate the dependence of the largest peak values on horizontal and vertical directions and on source-to-site distance.