Building 3D shear velocity models using surface wave testing: the Tarcento Basin case history

The paper reports on the use of surface‐wave testing for the construction of a three‐dimensional (3D) shear‐wave velocity model of an alluvial basin. The town of Tarcento (Italy) is located in a region with a high level of seismic hazard and was strongly affected by the two Friuli earthquakes in 1976. The seismic surveys were performed with surface‐wave multistation methods using a combination of active‐source and passive‐source experimental setup. Experimental data were collected at 16 sites, and inversion of the data is based on an innovative procedure for spatially constrained inversion with a single objective function in which a priori information is included. The method provides an improvement in the robustness of the solution, mitigating solution nonuniqueness. Available borehole logs at different locations are integrated into the data set in terms of a priori bedrock information. Three independent cross‐hole tests are used for a posteriori comparison of the inverted one‐dimensional (1D) profiles. Three‐dimensional interpolation of the obtained profiles leads to a shear‐wave velocity model that is internally consistent and complies with a priori information, cross‐hole results, and suitable boundary profiles. The model is intended for numerical simulations of the seismic response of the basin.