Building 3D Shear-Wave Velocity Models Using Surface Waves 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 bore-hole 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.