Abstract: Throughout its history, Portugal Mainland and Azores Archipelago have suffered the catastrophic effects of earthquakes originating significant damages in buildings and human losses. Being aware of Portuguese seismic risk, civil protection authorities promoted some studies leading to the development of a seismic scenario simulation tool, applicable to some Mainland Portuguese regions. This paper describes recent improvements in the seismic scenario simulation tool, named LNECloss, and illustrates its applications to the evaluation of building damages and social losses, due to plausible seismic scenarios affecting Portugal. Some development requirements were identified in LNECloss simulator, namely making it available as a service on the Web, providing a stand alone tool, with no need of a geographic information desktop environment, although with the GIS capabilities of mapping and synthesis of the seismic scenario effects. In conclusion, the developed GIS Web Service offers a useful tool for seismic risk assessment and emergency planning and management.