This article presents the Structural Health Monitoring System of the Central Tower at the Faculty of Physical and Mathematical Science of the University of Chile. The building has been continuously monitored since 2009 with a network of 8 uniaxial accelerometers and 17 environmental sensors that register ambient conditions, like wind speed and direction, temperature, rainfall, ambient and soil humidity. During this period, it has been continuously monitoring ambient vibrations and more than 1700 seismic events of different intensity. The building is a nine stories, 30 meters high, shear wall reinforced concrete structure. An automatic system is presented that identifies seismic response from continuous vibration records. Ambient vibration and noise are clearly identify and separated from seismic signals. Modal parameters are obtained from seismic records using different multiple input multiple output (MIMO) techniques. This article presents the analysis of 1700 seismic events recorded since 2009. The variation of the predominant frequency and damping is clearly identified as a function of level of shaking. Variations of these parameters are not related with damage and because of this are reversible. The magnitude of these variations are determined and compared with the variations cause by ambient effect (temperature, rain, humidity, radiation and others). The building exhibit damaged during Mw=8.8 2010 Chile earthquake. Window analysis of the response records show clearly the time of initiation of damage and its effect during the strong shaking and during aftershocks.