Exploring the Subsurface of Urban Areas with Distributed Acoustic Sensing (DAS) Deployed on Dark Fiber Networks

Session: Photonic Seismology [Poster]
Type: Poster
Date: 4/30/2020
Time: 08:00 AM
Room: Ballroom
Description: 

Characterization of the top several tens of meters of the subsurface is crucial for understanding a variety of earth phenomena such as ground shaking and surface deformation. This is particularly important in urban areas, where these processes can pose a significant hazard to built infrastructure and human lives. Seismic studies are commonly used to investigate near-surface seismic velocity structure, from which quantitative estimates of soil properties can be derived. In populated areas, however, executing seismic surveys can be challenging. Survey acquisition campaigns are often limited by access, in terms of both location and duration. Active surveys and long-term deployments are costly, and the coverage of current permanent arrays is sparse. These limitations result in missed information that can lead to unidentified hazards.

Here, we investigate the potential of combining Distributed Acoustic Sensing (DAS) and unused, pre-existing telecommunication fiber-optic cable networks (dark fiber) for the acquisition and analysis of ambient seismic noise generated in urban areas. DAS deployed on dark fiber enables a cost-efficient way of recording the seismic wavefield at high resolution at frequencies ranging from mHz to kHz for long distances (10s of km) and at a dense spatial sampling (~1 m). Anthropogenic ambient seismic noise recorded in two urban arrays within the cities of Berkeley and West Sacramento (California) is analyzed. Spatial and temporal variability of noise sources are investigated, and ambient noise interferometry approaches at different frequencies are applied to extract profiles of shear-wave velocity along the arrays. The feasibility to identify and characterize hazardous structures such as fault zones is also explored. Our observations will shed light into the opportunities and challenges offered by DAS deployed on dark fiber networks and its potential as a monitoring tool for hazard evaluation in highly populated areas where classic deployments are unfeasible.

Presenting Author: Veronica Rodríguez Tribaldos

Authors