## 4 The Role of S2 HM on SR  
Seismic structural health monitoring (S2 HM) plays an important role in the description of the state of a structure in pre-earthquake circumstances. In particular, the S2 HM has been significantly improved over the last decades, as shown in [38], by considering different techniques, such as novel algorithms that consider structural damage-sensitive features (e.g., inter-story drifts [39], frequencies [40], and nonlinear mode shapes [41]) that may be applied to detect damage due to earthquakes. These techniques may be implemented in numerical models, as shown in [42]. In particular, the principal stakeholders may apply such techniques to organize the emergency procedures and recovery process. In this regard, [43] investigated the value of information (VoI) in the case of long-term structural health monitoring, providing a rational basis to rank measuring systems, including the decision-making process affected by the monitoring campaign. Moreover, [44] proposed a framework that allows the optimization of structural risk and integrity management by considering fatigue deteriorating structural systems and their characteristics in order to demonstrate how inspection strategies can be performed. In addition, [45] considered the VoI framework to assess the use of visual inspection to support decision-making procedures in managing buildings. In addition, [46] considered the possibility of applying mutually VoI and structural health monitoring. Recently, [47; 48] considered the application of the probabilistic-based methodology of fragility curves to the assessment of seismic emergency  
Figure 1: Calculation of SR.  
procedures. In particular, [47] considered proposed to apply the Vol from Bayesian decision theory to convince stakeholders of the importance of S2 HM. In [48], the importance of inspections to improve the prediction of gradual and shock deterioration processes was considered.  
In this background, the accuracy of S2 HM is considerably important for the definition of seismic resilience. Therefore, DT is assumed herein to depend on the S2 HM, and thus several levels of accuracy were proposed herein. This principle consists of considering S2 HM fundamental tools for the definition of the procedures that follow the immediate occurrence of the earthquake. However, considering that the various uncertainties due to the extreme variability of structural typologies cannot be represented by factors, DT was herein considered proportional to \(RT\):  
\[\text{DT}=\lambda\cdot RT \tag{2}\]  
The coefficient \(\lambda\) may define several levels of accuracy in the general assessment of the conditions of the building due to the S2 HM. For example, Table 1 quantifies the coefficient \(\lambda\) on the basis of four levels of S2 HM accuracy (L1, L2, L3, and L4), named Slight, Moderate, Extensive, and Complete, proposing to consider DT as 50%, 35%, 20% and 5% of the RT. In particular, these four limit states were assumed to be similar to the approach proposed by [49] for the definition of loss models. It is worth noting that this formulation is a first attempt to assess the role of S2 HM in the definition of the delay time by considering that DT depends on several contributions, such as inspections, site preparation, eventual relocation of people and activities, engineering services, obtaining permits, securing financing and recovery activities, as in [8,10].