Passive seismological approaches for localizing near-surface fiber-optic cables with DAS

Accurate knowledge of existing fiber-optic cable geometry is essential for applications of distributed acoustic sensing (DAS), however the true positions of buried or installed fibers are often uncertain due to slack, bends, or deviations from documented routes. We present two passive, seismology-based approaches for cable localization that exploit information contained in DAS recordings. Case A employs ambient noise cross-correlations with reference points to estimate relative travel times, whereas Case B uses the differential arrivals of plane waves from distant earthquakes with linearly independent slowness vectors. Both approaches can be formulated in a least-squares framework that allows for the joint estimation of propagation velocity and geometry, thereby reducing biases from noise and model assumptions. Synthetic experiments show that cable positions can be recovered with an accuracy better than 100 m, even when apparent velocities are uncertain or the medium exhibits heterogeneity. The two methods provide independent geometric constraints that complement other sources of information on cable routing.