Evaluating the risk of natural disasters is an intensely debated issue, both on national and international level. In the present paper, after a brief review of the international research in this field and an introduction in risk management, we insisted on risk analysis of an urban area, called urban system. More precisely, we investigated the evaluation of risk and the behavior of the pipelines infrastructure characteristic in an urban area during an earthquake.By taking into account a certain region in Jassy city area, we present a methodology of evaluating seismic risk of the utilities network of the region. The method consists in establishing the necessary steps to be taken in such an evaluation. These steps are also graphically displayed for the gas pipelines of the area, and emphasizing the critical points existent in that sector e.g. gas stations). Using the cellular automata technique, inspired from the artificial intelligence and complex system fields, based on the GIS map of the analysed region, we obtained a map with the risk areas in case of an earthquake, taking into account the gas pipelines network and the existing critical points.