Reliability of Building Inventories in Seismic Prone Regions

A study on uncertainties in building inventory and vulnerability assessment for the city of Basel, Switzerland a moderate hazard but high-risk area is presented. Emphasis is put on the special conditions and demands on the data assessment procedure in such an environment. The building information was assessed from the sidewalk using a method similar to that proposed in FEMA-154. With only three persons working for two weeks, about 10% of the city’s building stock was assessed. The quality of the dataset was tested by using pre-existing reference data. These tests revealed patterns of misinterpreted structural information; important features like the floor type in URM buildings were difficult to identify.Six methods are proposed to derive building vulnerability from the collected structural information using the definitions of EMS98. The variation between the individual results was investigated in detail. A sample earthquake scenario with intensity IX in the city of Basel is used to demonstrate the influence of uncertainty in the inventory on the scenario results. The range of variation in the results is huge. Overall damage in the six scenarios differed by up to 27%. The amount of collapsed buildings in the historical part of the city comprised between 28% in the worst case and 3% in the best. There is a distinct influence of the inspector’s opinion visible in the scenario results, which introduces a remarkable uncertainty. This emphasizes the importance of reliable inventory assessments and makes uncertainty analysis in earthquake scenarios indispensable – especially in areas of moderate seismicity where observational data from earthquake damage is missing.