## 3 Description of the Case-Study Hospital Building
### As-Built State of the Hospital Building
The HVSR curve computed for the measurements performed in the immediate vicinity of the hospital building (FF_OBDD_1; FF_OBDD_4; FF_OBDD_5; FF_OBDD_6 and FF_OBDD_7) is flat, i.e., it has values lying between 0.5 and 2.0 (where a value of 1 is theoretically expected for a pure base rock outcrop) and without any clear peak within the wide range of frequencies (from below 1 Hz to up to a minimum of 25 Hz), which is typical of rock sites or rock-like geological formations with possible thin layers of weaker material at the surface, and can be therefore classified as ground type A according to Eurocode 8 [29]. The results of two measurements performed on the locations that are the furthest away from the location of the building (FF_OBDD_2 and FF_OBDD_3) differ from the results of the measurements performed in the immediate vicinity of the building, indicating the possible lateral variations of the soil characteristics (Figure 6). Figure 5: Minimal reinforcement in walls [30]. Figure 6: **(a)** Locations of ambient noise measurements performed on the site of the hospital building. Red arrow indicates the orientation of the instrument, which was the same for all measurements [32]; **(b)** horizontal to vertical spectral ratio (HVSR) curves computed for the individual free-field measurements performed in the vicinity of the building. Red line displays the averaged HVSR spectra and black lines display a confidence interval of 95%. In addition, a continuous instrumental monitoring of the building was also performed using a seismometer and the data acquisition system installed on the sixth floor with the sensor oriented along building's longitudinal direction, for a time period of 98 days (more than three months). These measurements were used to monitor its structural integrity and response to ground shaking induced by an earthquake. Unfortunately, no continuous measurements in the nearby free-field were performed. However, ambient noise measurements were performed in the free-field in the vicinity of the building on several locations, and the HVSR curve computed for these measurements is flat without any clear peak within the wide range of frequencies from below 1 Hz to up to a minimum of 25 Hz (see Figure 6). This means that the uncorrected spectrum measured on the sixth floor should be representative of the building's response. During this time period, a valuable high-quality data set was collected, which enabled the monitoring of fluctuations of the building's fundamental frequency. The spectrograms computed for two horizontal components (longitudinal and transversal) clearly indicate the first three modes of the building's dynamic behavior which are in excellent agreement with the results obtained by the OMA analysis (see Table 1). Moreover, continuous measurements enabled insight into the long and short term variability of the building's fundamental frequency. The long term variability of the frequency for the first three modes is observed for both components. This variation might be correlated to the seasonal change of distinct meteorological parameters. Unfortunately, since there is no meteorological station in the immediate vicinity of the building, a more detailed analysis in the sense of correlating observed fluctuations to weather conditions could not be done. Short term variations are linked to the change of the amplitudes of the excitation. This is clearly displayed on the spectrogram for two horizontal components of the recording made during one week (Figure 7). Noticeable differences were observed between the working hours (characterized with higher amplitudes in red color) and more quiet periods during the night (characterized with lower amplitudes). During the time period when continuous measurements were performed, there was no earthquake strong and close enough to cause damage to the building, nor any other events that had caused a change in the building's structural state of health.