In the emergency phase following a severe seismic event, it is essential to quickly proceed with the assessment of the damage suffered by buildings, both to assess which structures are still usable and to promptly intervene on damaged structures in order to prevent them from further damage. Damage data is also very important for the scientific community as it allow the creation of fragility curves for groups of buildings with homogeneous vulnerability and to carry out risk mitigation studies. The Department of Italian Civil Protection has developed, for each type of building (residential buildings, long-span buildings, churches, historic buildings), survey forms to collect the damage reported by the structures in a standardized way.

This paper is focused on the form used for churches (AD-C2006 form), that analyzed the seismic behavior of a church by considering each macro-element that composes it independently (i.e. façade, nave, apse, transept ...). The form proposes for each macro-element a variable number of collapse mechanisms, for a total of 28.

The analyses presented here concern the data of 225 churches inspected during the 2016-2017 Central Italy seismic sequence. All the churches were investigated twice by different technicians due to the occurrence of a second seismic event that required a further inspection. This chance has allowed to compare the data of two inspections relating to the same church and it highlighted the presence of frequent interpretative differences: often the collapse mechanisms identified by one technician did not coincide with those identified by the other technician. Each of the 225 churches was therefore carefully analyzed to identify the recurring situations that caused these critical issues.