3D P-wave and S-wave velocity model for the characterisation of the subsurface beneath the village of Arquata del Tronto (central Italy)

The geophysical characterisation of the subsurface in areas affected by strong earthquakes is a fundamental practice, which enables the correct assessment of seismic hazard and risk. In this study, we have considered the area of the historical centre of Arquata del Tronto (central Apennines, Italy), which was destroyed by a strong earthquake in 2016. A three dimensional (3D) P-wave and S-wave velocity model was defined and the model was obtained from first arrival tomography, computed on a seismic survey consisting of three lines hugging the hill where the old village was located. The velocity model and, especially, the VP /VS ratio show some interesting aspects, indicating in particular some anisotropic features present in the area due to the existence of flysch formations characterised by the alternation of sandstone, pelite, and marl in different proportions. In this analysis, the vertical seismic profile data acquired in a 100-metre deep borehole was also considered. The P-wave and S-wave vertical velocities were compared with the vertical velocities extracted from the 3D tomographic model at the same point of the well.