Seismic characterization and monitoring of Fucino Basin (Central Italy) |
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Authors: | F Cara G Di Giulio G P Cavinato D Famiani G Milana |
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Institution: | 1. Sezione Sismologia e Tettonofisica, Istituto Nazionale di Geofisica e Vulcanologia, Via di Vigna Murata 605, 00143, Rome, Italy 2. Istituto di Geologia Ambientale e Geoingegneria, Consiglio Nazionale delle Ricerche, Via Salaria Km 29,300, 00016, Monterotondo Stazione, Rome, Italy 3. Dipartimento per lo Studio del Territorio e delle sue Risorse, Universit?? degli studi di Genova, Corso Europa 26, 16132, Genoa, Italy
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Abstract: | The Fucino basin (Central Italy) is one of the largest intramountain alluvial plain in the Apennines range. It has a tectonic
origin related to the presence of important systems of faults located in its northern and eastern edges. Some of these faults
are still active and capable of generating strong seismic events. Site effects related to the soft soils filling the basin
can be very important. In this paper we show the preliminary results of a seismic network installed in the Fucino area in
order to collect information about site amplification effects and geometry of the basin. We analyze ambient seismic vibrations
and recordings of about 150 local earthquakes mainly related to the seismic sequence of the April 6th 2009 Mw 6.3 L’Aquila
event. Moreover the strongest events of L’Aquila sequence were analyzed at the three permanent strong-motion stations operating
in the area. Using standard spectral techniques we investigate the variation of resonance frequencies within the basin. The
ground motion recorded in the Fucino plain is mainly characterized by strong energy at low-frequencies (f < 1 Hz) affecting both horizontal and vertical components. This is particularly evident for stations deployed in correspondence
of very thick deposits of sedimentary filling, where a significant increase of ground-motion amplitude and duration is likely
caused by locally generated surface waves. The amplification at low-frequencies (<1 Hz) on the horizontal components can reach
up a factor of 10 in comparison to nearby stiff sites. However, we found evidences of seismic amplification phenomena also
for stiff sites surrounding the basin, including stations of the Italian strong motion network. The independent geological
information and the shallow shear-velocity profiles available for the basin can be combined with resonance frequencies for
deriving representative geological sections to be used as base for future numerical 2D–3D modeling of the basin. |
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