Seismic amplification in a fractured rock site. The case study of San Gregorio (L'Aquila, Italy)

Publication date: Available online 6 August 2016 Source:Physics and Chemistry of the Earth, Parts A/B/C Author(s): Di Naccio Deborah, Vassallo Maurizio, Di Giulio Giuseppe, Amoroso Sara, Cantore Luciana, Hailemikael Salomon, Falcucci Emanuela, Gori Stefano, Giuliano Milana The village of San Gregorio (SG), eight kilometres away from L’Aquila (central Italy), was severely damaged by the April 6, 2009 L’Aquila earthquake (MW 6.1). A coseismic fracture zone was mapped along SW-dipping fault segments crossing SG, which is situated at the base of a carbonate relief bounded by the Aterno river alluvial plain. An interdisciplinary approach was used to investigate the seismic response of the area based on geological-structural, geophysical and seismic analyses. We integrated our data with available information from the recent microzonation studies. SG is partly built on alluvial fan deposits constituted by cemented gravel, and partly on jointed carbonate bedrock. An extensive survey of noise measurements showed strong and polarized peaks in the horizontal-to-vertical spectral ratios (H/V), both on soft and rock sites in the 2-10 Hz frequency band. Further, we checked the stability with time of H/V ratios at three sites of SG. An analysis on local earthquakes confirmed the results of noise measurements. To understand the influence of rock mass jointing condition on site effects, we performed structural surveys on carbonate bedrock. We also evaluated the propagation velo...

Source: Physics and Chemistry of the Earth, Parts ABC - August 6, 2016 Category: Science Source Type: research