Automatic selection of modal parameters from stability diagrams is a requirement for automatic SHM systems and damage assessment. In the present article we describe and apply a methodology of an automatic modal selection based on data recorded continuously for 5 years in a building structure located in Chile. The building has been subjected to more than 1,700 earthquakes. Environmental conditions and noisy signals are present on the data and identified modal parameters. The methodology considers soft and hard discriminants between real and spurious modes. Evaluation of the methodologies is done based on the effectiveness of the discriminants and the computational cost of its evaluation. Results indicate that the parameters should be selected based on the number and type of sensors, noise level on the data, modal properties and damage characteristics of the structure.