Publication Date:
2024-05-22
Description:
The application of ambient seismic noise tomography to continuous dynamic strain data recorded along existing fiber-optic cables using Distributed Acoustic Sensing (DAS) is emerging as a promising approach for cost-efficient, regional-scale (10’s of km) subsurface imaging and monitoring at high spatial (~1 m) and temporal resolution in a variety of environments. Ambient noise dispersion-based methods have gained significant attention in recent years, and they have been successfully applied to retrieve detailed subsurface velocity models both onshore and offshore. Yet, these methods are limited by the assumption of negligible lateral variations across the array segment analyzed to extract dispersion curves. The length of the segment constrains not only the spatial resolution of the resulting 2D velocity model, but also the maximum depth of investigation. The high density of measurements provided by DAS datasets, however, enables resolving small-scale, lateral velocity variations when analyzed using approaches that are not scale-limited. Here, we investigate the application of alternative ambient seismic noise methods to dynamic strain data recorded along dark fibers in urban areas to constrain shear-wave velocity models obtained using dispersion-based techniques. In particular, we explore the potential of autocorrelation methods (i.e., single-channel cross-correlations) for resolving fine-scale subsurface structure and exploring wave propagation characteristics associated with it. We apply these methods to continuous ambient seismic noise recordings from dark fiber DAS campaigns conducted in Berlin and Potsdam (Germany) to complement seismic exploration activities for urban geothermal projects. Challenges associated with the complexities of the urban seismic noise field and their influence on autocorrelation results will be discussed. For the Potsdam dataset, results will be compared against seismic reflection images obtained from a conventional, controlled-source seismic experiment using geophone arrays whose trajectories followed the dark fiber profile closely. Ultimately, we aim at providing insights into how we can use dark fiber DAS recordings of the ambient seismic noise field to understand the heterogeneity of the urban subsurface.
Type:
info:eu-repo/semantics/conferenceObject
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