Urban subsurface monitoring requires a system with high temporal-spatial resolution, low maintenance cost, and minimal intrusion to urban life. Distributed acoustic sensing (DAS), in contrast to conventional station-based sensing technology, has the potential to provide a passive seismic solution to urban monitoring requirements. Based on data recorded by the Stanford Fiber Optic Seismic Observatory, we demonstrate that near-surface velocity change induced by the excavation of basement construction can be monitored using existing fiber optic infrastructure in a noisy urban environment. To achieve the superior results, careful signal processing with noise removal and source signature normalization are applied to raw DAS recordings. The repeated blast signals from quarry sites provide free, unidirectional, and near impulsive sources for periodic urban seismic monitoring, which are essential for increasing the temporal resolution of passive seismic methods. Our study suggests that DAS will likely play an important role in urban subsurface monitoring. [link to publication]