8.1 Earthquake 16/09/2004
The acceleration of the northern region of the base of the dome along E - W direction is higher than the acceleration of the southern region. The acceleration of the west region of the base of the drum is higher than that of the east region. Period of the longitudinal and transversal translational modes were not changed during the earthquake. On the cornice the acceleration of the south - west corner along E - W direction is higher than the acceleration of the north - east one. The drum was mainly deformed and consequently the acceleration on the base of the dome was increased.
8.2 Earthquake 08/01/2006
The period of the monument along E - W direction was 0.27 sec at the beginning of the earthquake and it was found to be 0.30 at its end. The period along N - S direction was 0.32 sec and it was changed to 0.39 sec. Consequently, the stiffness of the structure was changed, probably due to a further deterioration of the damaged structure, as no intervention was yet implemented.
8.3 Earthquake 05/11/2006
This specific earthquake occurred three months after the completion of the first period of grouting during which injections were implemented to almost the half of the height of the perimeter walls. Periods and damping along both main directions were found to be lower. The dynamic characteristics of the structure did not change during the earthquake. These results show that, although only half of the structure has been repaired by means of hydraulic lime grouting injections, the effect
of grouting was clearly distinguished, as the dynamic characteristics of the structure have changed.
8.4 Earthquake 12/12/2006
This specific earthquake occurred almost one month after the previous one, four months after the completion of the first period of grouting. There was no other new element that could have affected the characteristics of the monument except the evolution of grout hardening. The period of the structure was the same along the N-S direction, while along E-W direction a very slight increase was recorded during the earthquake. The damping of the structure was higher than that of the previous event but it remained lower compared to the damping before the first period of injections.
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