GNGTS 2024 - Atti del 42° Convegno Nazionale

Session 3.2 GNGTS 2024 Fig. 2 – Complete 3D Vp model from the travel tme tomography of the three lines. a) 3D view. b) Vertcal sectons extracted along the east-west directon and spaced 25 m apart (see map top right). c) Vertcal sectons extracted along the north-south directon and spaced 25 m apart (see map top right). For each line, we inverted the travel tmes of the frst arrivals , which were treated as related to diving waves in the ray tracing used for the inversion. The resoluton of the fnal tomographic models for Lines 1 and 2 is 2.5 m both in horizontal and vertcal directons, startng from a base grid of 10x10 m (horizontally), while for Line 3, the resoluton of the fnal velocity model is 5 m (horizontally) per 2.5 m (vertcally), startng from a base grid of 15x15 m (horizontally). For each inversion, the reliability of the tomographic soluton was checked by analysing the tme residuals (diference between the observed travel tmes and those calculated on the fnal model). In all instances of inversions based on the P tmes, root mean square (rms) values for the tme residuals were approximately 3.5% in relaton to the observed tmes. This corresponds to about 2.3 ms for Line 1, 3.1% with 1.3 ms for Line 2, and 1.6% along with 1.5 ms for Line 3 (which exhibited the lowest residuals).