Seismic activity began to slightly increase during the construction but rose sharply upon the completion of the tallest building in the world, the Taipei 101, which stands at 508 m in the Taipei basin, where local seismicity had historically very low. Besides an increase in both seismic energy and the number of micro-earthquakes, two felt earthquakes astonishingly occurred beneath the completed building. The focal mechanism of the larger felt earthquake and its aftershocks are indicative of an active blind normal fault just beneath the building. Estimations of the vertical loading of the Taipei 101 show that local stress on its foundation increased at least 4.7 bars, making it seem likely that the increased seismicity was a direct product of the loading of the mega-structure. Further investigations in unison with continuous seismic monitoring must be conducted because the safety of the high-rise building in the Taipei basin be comprehensively assessed.