GNGTS 2024 - Atti del 42° Convegno Nazionale

Session 1.3 GNGTS 2024 will also consider two parallel families of models, one with a Maxwell mantle, and a second one with an Andrade (1910) mantle. Our goal is showing the role of every parameter in the determinaton of the response functon or, in other words, the displacement. In partcular, we will try to establish which combinaton of forcing period and load extent leads to the largest phase lag between the load history and the consequent response. As a preliminary experiment we performed a series of tests using the Earth Model from Barleta (2006). This model presents a thin elastc lithosphere of 18.5 km and 5 viscoelastc layers of diferent viscosites (see Tab. 1). Firstly, with the ALMA code (Melini et al. 2022), we analysed the complex Love Numbers h and l associated with this model. Partcularly, we were interested in the phase lag, namely . This quantty is of great interest since, through the relaton , where Q is the quality factor and the tdal angular frequency (Tobie et al. 2019) , it allows us to evaluate the tme delay between the load signal and the Earth’s response. Results are shown in Fig. 1, where the plots display a quite complicated behaviour: the vertcal Love number h presents, up to degree n = 100 , a double-peak behaviour, while for higher degrees one peak only is observed. However, it is apparent that the more substantal phase lags occur for periods within 10 0 kyr < T < 10 2 kyr . By looking at the horizontal Love Number instead, we can clearly distnguish that, especially for degrees n > 10 and for shorter periods ( 10 -1 kyr), large phase lags are stll visible. Next, using the Taboo code (Spada et al. 2004) we computed the response of the model to a single disc load of semi amplitude = 1.5° with a sinusoidal tme history in which the ice height fuctuated between a maximum value of 10 m and a minimum of 0 m . We tested the sensibility of this model to diferent forcing periods, and we pushed our analysis up to the harmonic degree 128 . As we can see from Fig. 2, the fndings of our previous analysis are confrmed: for periods of the order of 10 0 kyr the tme lag between the load and the surface response is clearly visible, while for shorter forcing periods only horizontal displacements seem to preserve a distnguishable tme lag. tan ( ϕ ) = − Im [ L n ( ω )]/ Re [ L n ( ω )] Δt = arcsin ( Q −1 )/ ω ω ∼ α