DAMAGE IN ANCIENT CHURCHES DURING THE 9TH OF JULY 1998 AZORES EARTHQUAKE

SUMMARY In the 9 th of July of 1998, an earthquake of magnitude 6.2, on the Richter scale, occurred in the Azores Islands. The earthquake was registered in almost all the islands of the archipelago but with structural damage occurring mainly in the Faial and Pico islands. Massive damage occurred, with intensities larger than VIII in the Modified Mercalli scale. Some villages were almost completely destroyed. This paper focuses on the earthquake performance of ancient churches of the Faial and Pico islands and aims at describing and interpreting the most significant types of damage sustained by this type of unreinforced stone masonry structures, with large exterior walls, inner arches and light wooden roofs. The study presented on this paper is based on the in-situ damage observation on 30 churches. The damage modes and possible collapse mechanisms were identified to all the churches and the damage level of each one were quantified based on a set of indicators. The observed damage was correlated with the structural typology, with the quality of the construction and with past interventions suffered by the churches. The observation of the different constructions allowed the clear identification of typical patterns of structural damage. These patterns and the observed damage levels are very dependent on the seismic action level, on the quality of the masonry used in the constructions and on the existence of structural interventions made in the sequence of previous seismic events.