GNGTS 2022 - Atti del 40° Convegno Nazionale

258 GNGTS 2022 Sessione 2.2 δ max,i : absolute value of the maximum displacement for a seismic sequence (seq) or the corresponding main shock (main); n°seq j : total number of sequences in a certain j-th group. • (2) in which: δ max,+,i : maximum positive displacement for a seismic sequence (seq) or the corresponding main shock (main); δ min,-,i : minimum negative displacement for a seismic sequence (seq) or the corresponding main shock (main). • (3) in which: Δ δ : = δ max ,+ – δ min ,– (4) M1 δ , by considering the maximum absolute value of displacements, leads to the lower indicator. It is higher than 1 only on the inelastic phase, so providing an indication on the increase of ductility demand due to the seismic sequences. On the contraryM2 δ , by considering the maximum ratio between maximum positive and minimum negative displacements, leads to the higher indicator. M3 δ , by estimating the maximum displacements excursion, leads to a medium value. Fig. 2 - a) Natural sequence of Friuli-Forgaria Cornino; the 6 th signal is considered as the main shock; b) Comparison between dynamic cycles from seismic sequence and main shock for the case of Friuli-Forgaria Cornino. a) b)