A geology-based 3D velocity model of the Amatrice Basin (Central Italy)

The Amatrice area was historically affected by moderate to large earthquakes, which caused extensive damages and many casualties, like the 1639 and the 2016-2017 seismic sequences. For this reason, the area was extensively studied and a large amount of seismological, geological and geophysical data were acquired. However, a detailed 3D geological model of the area subsoil was still missing and, consequently, the local seismic response evaluation of the area could only be based on the geological and geotechnical characteristics of rocks and the available low-resolution and large-scale models. In this work we present a new methodological approach integrating geological (e.g., maps, cross-sections and core-wells) and geophysical (e.g., down-hole, MASW, refraction, and seismic noise measurements) data applied for reconstructing a detailed 3D geological and geophysical model of the uppermost hundreds of meters of the Amatrice Basin. All the available data were georeferenced and uploaded into 3D geological modeling software where faults and stratigraphic boundaries were digitized, checked, hierarchized, and modelled. The reconstructed 3D geological model was parameterized with the S-wave (Vs) and P-wave (Vp) velocities values, and the resulting 3D geology-based velocity model was verified by comparing the environmental noise (i.e., horizontal-to-vertical spectral ratio analysis, HVSR) recorded at some seismic stations with the seismic responses modelled at some nearby control points. The proposed model is the first geology-based 3D velocity model of the Amatrice Basin, which may be used for example as input-model for future ground-motion and seismic-wave-propagation simulations aimed at a more precise local seismic response assessment and, consequently, at the development of more realistic seismic hazard scenarios. The methodological approach here presented can also be applied in other areas for reconstructing detailed 3D geological-geophysical models to be applied for the assessment and mitigation of different geological risks.