Measurement of seismic local effects and 1D numerical modeling at selected sites affected by the 2009 seismic sequence of L’Aquila

Strong local effects occurred during the seismic sequence that affected the area of L’Aquila (Central Italy) in 2009, which culminated with a main shock of magnitude (Mw) 6.3 on the 6 April. Bearing in mind the magnitude, the vicinity of a regional capital to the epicentre, the presence of several historic centers and villages, which caused significant damage (IMCS max=9.5) and approximately 300 victims, among the main characteristics of this earthquake, was the variability of the recorded damages within the scale of 100 m in spite of the near field conditions and a distinct source mechanism. These local effects were measured with an array of geophones at selected sites near the city of L’Aquila. In one of the sites, located at Onna village which experienced maximum damage levels, the 1D numerical modeling allowed verifying the influence that the frequencey of the input motion has in the determination of superficial seismic effects. The numerical modeling, which was undertaken on the basis of the results from geomechanical, seismic and geoelectrical surveys, also allowed verifying that underestimation of local seismic amplification can be introduced by the current regulatory framework (Italian seismic regulatory guidance “Norme Tecniche per le Costruzioni” – D.M. of 14 January 2008) in contexts similar to that of L’Aquila.