Urban Sensing Using Existing Fiber-Optic Networks

The analysis of urban seismic sources offers valuable insights into urban environments, including seismic hazards, infrastructure conditions, human mobility, and cultural life. Yet, accurate detection and localization of seismic sources at the urban scale with conventional seismic sensing networks is unavailable due to the prohibitive costs of ultra-dense seismic arrays required for imaging high-frequency anthropogenic seismic sources. Here, we leverage existing fiber-optic networks as a distributed acoustic sensing system to accurately locate urban seismic sources and estimate how their intensity varies with time. By repurposing a 50-kilometer telecommunication fiber into an ultra-dense seismic array with 50,000 channels, we generate high-resolution spatiotemporal maps of seismic source power (SSP) across San Jose, California. Our approach overcomes the proximity limitations of urban seismic sensing, enabling accurate localization of remote seismic sources generated by urban activities. Examples of detected activities are vehicle movements and operations at construction sites and schools. We also show strong correlations between SSP values and noise level measurements, as well as various persistent urban features, including point of interest density, land use patterns, and demographics. Our study shows how spatiotemporal SSP maps can be turned into novel urban data that effectively captures urban dynamics across multiple features, thus opening the way towards the use of fiber-optic networks as a ubiquitous and general-purpose urban sensing platform, with wide-ranging applications in urban and environmental studies.