Eartquake in Rome and geology in Rome evidenced by web-based macroseismic intensity survey of main eartquakes of l Aquila sequence,

During L'Aquila earthquake sequence, a detailed macroseismic analysis was conducted in Rome, where a large amount of data was collected from web-compiled questionnaires (3695 reliable questionnaires). We consider people and buildings as instruments recording seismic effects such as shaking intensity, movements of objects, human reactions and damage: all these information were collected in real time via our web site www.haisentitoilterremoto.it .Although Rome is settled in a relatively low-seismicity area, in the past, it suffered damage produced by earthquakes occurring mainly in the Alban Hills and in the central Apennines. We expect that local site amplification of the analysed earthquakes will be the same for a larger event occurring in that area. Data regard low intensity degrees, characterised mostly by transient effects recorded by people all over the urban area located at a distance ranging from 75 to 110 km from the epicenters. All intensity data were normalised for each event by subtracting the mean intensity for Rome city and by compensating the attenuation effect with distance from the hypocentre. Stacking and spatial filtering procedures were applied to intensities of all events, obtaining a filtered and interpolated residual map. Intensity residuals were compared with detailed geological reconstructions. Good agreement is found between amplification areas of Rome urban territory and geology. We also put in evidence the deep geology role as important as near surface geology for the definition of some amplifications areas. Moreover we reveal some amplification areas unknown by historical macroseismic observations in Rome, due to intense recent urban expansion.