2D versus 1D ground-motion modelling for the Friuli region, north-eastern Italy

We perform a series of simulations of seismic wave propagation from potential earthquakes to evaluate how the 2D (in the NW-SE direction) geological structure of the Friuli (NE Italy) basin affects ground motions, particularly in terms of peak ground velocity (PGV). The decay of PGV with source-receiver distance from the 2D modelling is compared to that obtained from 1D modelling, using a standard model for seismological studies in this region, one obtained by averaging the 2D model along the source-receiver distance and one based on the local structure under the receiver. Synthetic seismograms are computed using a finite-difference technique for point sources with an upper frequency cut-off of 0.6 Hz. 2D effects are clearly seen, particularly in the centre of the sedimentary basin, for certain earthquake scenarios. The analysis of the role played by the main heterogeneities on the propagating wavefield permits us to conclude that an acceptable fit to the 2D PGV values for the entire section is possible using a series of 1D models for the Friuli region except for shallow earthquakes located to the north-west of the basin, where the structure of the basin edge is complex.