## 4 Results
### Relationships between Rainfall, Pore Water Pressure, and Subsurface Displacement  
The relationships between rainfall, pore water pressure, and deep movements have been investigated separately for each distinguished kinematics stage through the coupled analysis of monitoring data recorded by the sensors installed in the FON2 and P3 verticals (see Section 3.3). The displacement time-series pointed out that both the SM and IM stages showed a certain degree of correlation with rainfall distribution at the seasonal scale (see Section 4.3). However, the comparison between the trends in pore water pressure and cumulative displacement revealed that water pressure did not oscillate significantly at the examined sliding depth throughout these periods (Figure 17). This was testified by (1) the computed daily mean values of pore water pressure, which were very similar for all kinematics stages and consistent with the mean of the entire monitoring period (compare Table 5 and Figure 9a), and (2) by the statistical indices describing the variation in water pressure (Table 5), which indicated moderate fluctuations on both a seasonal and daily scale (see Section 4.2). Regarding the RM stage, daily rainfall and daily pore water pressure trends were analyzed in conjunction with those of daily cumulative displacement and daily displace  
Figure 17: Relationship between cumulative daily displacements, daily rainfall, and daily pore water pressure during the slow-motion (**a**) and inactive-motion (**b**) stages. In all panels, the fitted linear trends to daily cumulative displacement data are indicated. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{3}{*}{**Probe Id**} & \multirow{3}{*}{**Motion Stage**} & \multicolumn{6}{c}{**Pore Water Pressure Data**} \\ \cline{3-8}  & & \multicolumn{4}{c}{**Daily Value**} & \multicolumn{4}{c}{**Daily Change**} \\ \cline{3-8}  & & **Mean** & **Max** & **Min** & **St. Dev.** & **Max** & **Min** \\ \hline \multirow{3}{*}{P3} & SM1 & 12.5 & 15.0 & 10.0 & 1.3 & 2.0 & \(-1.0\) \\  & SM2 & 14.0 & 17.0 & 11.0 & 2.0 & 2.0 & \(-1.0\) \\  & SM3 & 15.7 & 18.0 & 12.0 & 1.6 & 2.0 & \(-1.0\) \\ \cline{2-8}  & IM1 & 13.8 & 16.0 & 12.0 & 1.1 & 3.0 & \(-1.0\) \\  & IM2 & 13.5 & 17.0 & 7.0 & 2.2 & 3.0 & \(-2.0\) \\  & IM3 & 15.3 & 19.0 & 12.0 & 2.8 & 1.0 & \(-1.0\) \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Summary of the most important pore water pressure statistics computed for each slow-motion (SM) and inactive-motion (IM) stage identified. ment rate (Figure 18a,b). It was observed that the two positive gradients of cumulative displacement matched with the pore water pressure peaks (Figure 18a), which in turn required a preparatory period of several days to be attained following the highest levels of daily rainfall (see Section 4.2). In general, these two phases of greater mobility appeared to follow rather similar styles. Indeed, cumulative displacements tended to increase simultaneously with pore water pressure growth; once initiated, motions progressively continued approaching pore water pressure peaks and then slowed down as the pore water pressure dropped (Figure 18a). However, the two motion sequences showed rather different behaviours in terms of displacement rates (Figure 18b). The first motion phase was characterized by a fairly regular series of accelerations and decelerations of similar magnitude and duration, as shown by the serrated profile in the graph of daily displacement rate. Interestingly, these changes in movement velocity developed despite the pore water pressure trend showing a general increase (Figure 18b). Conversely, the second phase of motion was characterized by a main sharp acceleration developed simultaneously with the increase in pore water pressure (Figure 18b). These two different motion dynamics may be correlated to the magnitude in pore water pressure variations.