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Urban subsurface monitoring requires high temporal‐spatial resolution, low maintenance cost, and minimal intrusion to nearby 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 changes induced by the excavation of a basement construction can be monitored using existing fiber optic infrastructure in a noisy urban environment. To achieve satisfactory results, careful signal processing comprising of noise removal and source signature normalization are applied to raw DAS recordings. 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.

Background To evaluate the ability of peripheral blood inflammatory markers in predicating the typing of COVID‐19, prognosis, and some differences between COVID‐19 and influenza A patients. Methods Clinical data on 285 cases laboratory‐confirmed as SARS‐CoV‐2 infection were obtained from a Wuhan local hospital's electronic medical records according to previously designed standardized data collection forms. Additional 446 Influenza A outpatients’ hematologic data were enrolled for comparison. Results NLR, SII, RLR, PLR, HsCRP, and IL‐6 were significant higher and LMR was lower in severe COVID‐19 patients than in mild COVID‐19 patients ( p < .001). PLR and LMR were lower in the individuals with influenza A than those with COVID‐19 ( p < .01). COVID‐19 patients with higher levels of NLR, SII, RLR, PLR, HsCRP, and IL‐6 and lower LMR were significantly associated with the severe type. AUC of NLR (0.76) was larger while the specificity of IL‐6 (86%) and sensitivity of HsCRP (89%) were higher than other inflammatory markers in predicating the typing of COVID‐19. PT had obvious correlation with all the inflammatory markers except RPR. NLR showed positive correlations with AST, TP, BUN, CREA, PT, and D‐dimer. Patients with high IL‐6 levels have a relatively worse prognosis (HR = 2.30). Conclusion Peripheral blood inflammatory markers reflected the intensity of inflammation and associated with severity of COVID‐19.NLR was more useful to predict severity as well as IL‐6 to predict prognosis of COVID‐19. PLR and LMR were initially found to be higher in SARS‐CoV‐2 virus‐infected group than in influenza A.