Fig. 3

Synthetic transfer functions (\({\mathbf {{D}}}_{xx}\)) comparing base (orange dashed box in Fig. 2) and measured (purple dashed box in Fig. 2) sites for Lines 1–6. The x-axis is the period in seconds. The blue transfer functions represent the baseline model, and red transfer functions result from the introduction of the 1 \(\Omega\)m conductive body at 3.6 km depth (represented by the red shaded rectangle). Note that only the real components of the transfer functions are plotted