The 3D basin effect on the seismic response estimation at sites with liquefiable layers: Case study of Volos basin (Thessaly, Central Greece)

The effect of a 3D basin structure on the seismic response of soil and its potential impact on liquefaction initiation was found to be highly significant, after conducting 3D numerical modelling for wavefield simulation and non-linear analysis. The Volos basin in Thessaly (Central Greece) was judged to be suitable for testing the 3D-effect of near-field propagating wavefields. Using the resulting synthetic data, non-linear analysis was performed for a specific number of coastal sites with low V S values and potentially liquefiable layers. Soil characterization and non-linear analysis were based on data obtained by seismic surveys that were carried out at the area, as well as local geological and past borehole data. Several earthquake scenarios from two local large faults were tested and by comparing the results obtained using the 3D basin model and the respective simple 1D layered model, it was proven that the 3D structure not only causes the amplification of the ground motion, but also highly affects the initiation of liquefaction in all tested cases. The effect of the 3D structure on the amplitude and duration of the calculated ground motion as well as on its frequency content is found to be significant for initiating liquefaction phenomena in such basin cases. • 3D site response of a small basin evaluated using numerical modelling. • Non-linear analysis reveals the effect of small basins on liquefaction. • Liquefaction initiation is highly affected by 3D basin morphologies.