Evaluation of site effects in the Aterno river valley (Central Italy) from aftershocks of the 2009 L’Aquila earthquake

Abstract

A temporary network of 33 seismic stations was deployed in the area struck by the 6th April 2009, Mw 6.1 (Scognamiglio et al. in Seism Res Lett 6/81, 2010), L'Aquila earthquake (central Italy), with the aim to investigate the site amplification within the Aterno river Valley. The seismograms of 18 earthquakes recorded by 14 of the 33 stations were used to evaluate the average horizontal to vertical spectral ratio (HVSR) for each site and the 123 698 Bull Earthquake Eng (2011) 9:697-715standard horizontal spectral ratio (SSR) between a site and a reference station. The obtained results have been compared to the geological and geophysical information in order to explain the resonance frequencies and the amplification levels with respect to surface geology of the valley. The results indicate that there is no uniform pattern of amplification, because of the complex geologic setting, as the thickness and degree of cementation of the deposits is highly variable.

Spectral models for ground motion prediction in the L'Aquila region (central Italy): evidence for stress-drop dependence on magnitude and depth

“…As already observed by other authors Bergamaschi et al 2011), the empirical functions found in this study confirm the large variability of the site response in the Abruzzo region that cannot be taken into account using simple site-classification based on geological information (Table 1). Furthermore, this study also confirms the relevance of the amplification on the vertical motions, indicating that in the L'Aquila region, the H/V ratio should be used with caution for evaluating the local site response.…”

“…The considered networks are: the National Seismic Network, RSN, operated by INGV (Istituto Nazionale di Geofisica e Vulcanologia); the Mediterrean Network, Mednet, operated by INGV; the Rapid Response Networks operated by INGV, RESIF (Reseau Seismologique and Geodesique Francais) and the University of Genoa; the National Accelerometric Network, RAN, operated by the Department of Civil Protection, DPC. We complete the data set by including data from temporary networks deployed for seismic microzonation (Working Group SM-AQ 2010), site effect studies (Bergamaschi et al 2011) and aftershock monitoring (Margheriti et al 2011). Details on instruments and stations of each network are listed in Table 1.…”

“…Site amplification effects are relevant for the L'Aquila data set (e.g. Bergamaschi et al 2011;Puglia et al 2011;Di Giulio et al 2014), since the epicentral area is located inside a river valley filled with quaternary deposits of various depths. Geological conditions are so variable that over a distance of few tens of metres the shear wave velocities of the shallower soil layers may differ substantially, as shown by the soil profiles available for some strong-motion stations from the Italian accelerometric archive (ITACA, http://itaca.mi.ingv.it; Luzi et al 2008;Pacor et al 2011).…”

Local variability of the ground shaking during the 2009 L’Aquila earthquake (April 6, 2009—Mw 6.3): the case study of Onna and Monticchio villages

“…Seismic data show that L'Aquila downtown is characterized by a clear resonance frequency at about 0.6 Hz (De Luca et al 2005;Milana et al, this issue) whereas in the Aterno river valley the fundamental frequencies can increase up to 5 Hz (Bertrand et al 2009;Bergamaschi et al 2011).…”

“…2). The seismic stations considered in this paper were installed for the evaluation of local amplification phenomena (Bergamaschi et al 2011) as well as in the framework of a national project (C.A.S.E project, where C.A.S.E stands for Anti-seismic, Sustainable and Environment-Friendly Buildings) aimed at the construction in the epicentral area of seismic-isolated buildings. Although the three villages are within a distance of 2 km from each other and the historical masonry buildings are supposed to share the same quality and characteristics, they suffered a different degree of damage (Galli and Camassi 2009).…”