On the Use of Web Mapping Platforms to Support the Seismic Vulnerability Assessment of Old Urban Areas

European countries are affected by various levels of seismic hazard, including many areas with medium to high seismicity. Heavy damage over large areas has been observed in past earthquakes in these countries, particularly in masonry buildings located in historical centers, confirming the need for enhancing the current knowledge on the seismic vulnerability of these constructions, so more informed technical and political decisions towards the mitigation of the risk can be taken. However, the characterization of building stocks for engineering purposes is still an open issue due to the enormous amount of resources that such a project would require. Nevertheless, the availability of virtual images and maps represents an outstanding opportunity for having remote approaches to urban environments. The role of on-site inspections can be complemented or even substituted by means of these remote approaches, provided it is complemented with suitable approaches. The use of these resources is not new, but the critical assessment of their capabilities and limitations deserves a critical discussion. The present paper aims at assessing the opportunities offered by web-based mapping platforms in the context of seismic vulnerability assessment of masonry buildings in old urban areas. After evaluating the advantages and shortcomings of some of the most popular web-based mapping services, an explanatory application to a set of 39 buildings located in the historic center of the city of Leiria (Portugal) is presented and critically discussed, contrasting the results obtained by using on-site and remote inspections. Two different seismic vulnerability assessment approaches are applied and analyzed herein, confirming that web-based mapping platforms can represent an efficient and cost-effective complement to traditional field surveys when the large-scale seismic vulnerability of old urban areas is of interest.