GNGTS 2024 - Atti del 42° Convegno Nazionale

Session 1.1 GNGTS 2024 (the more such logarithms are negatve, the stronger the atenuaton). Spectral amplitudes are estmated through peak values of narrowband-fltered tme histories: if fc is the central frequency, the bandpass flter is obtained by an eight-pole Buterworth low-pass flter with corner at , followed by an eight-pole high-pass flter with a corner at . Afer fltering, Random Vibraton Theory (RVT) is applied to peak values to produce an estmate of spectral amplitude, given the tme duraton of the analyzed signal. Details can be found in Malagnini and Dreger (2016), and references therein. Figure 3. Logarithms of total atenuaton experienced by direct S waves along the transitonal segment of the SAF at Parkfeld, between 4 and 12 km of hypocentral distance, at the indicated central frequencies of 42.2 and 50.0 Hz. With Figure 4 we try to extract more specifc informaton on two frequency bands at the two ends of the investgated spectrum: 2-5 Hz and 30-50 Hz. The quanttes shown in Figure 4 are the stacked atenuaton values that were calculated in the central frequencies contained in the 2 f c 1 2 f c