Filtering Strategies for Deformation-Rate Distributed Acoustic Sensing

Area of Science:

• Geophysics
• Seismic Exploration
• Fiber Optic Sensing

Background:

• Distributed acoustic sensing (DAS) theoretically captures seismic particle motion.
• Achieving elastic ground-fiber coupling is challenging in shallow horizontal deployments.
• Environmental factors impact the repeatability and quality of surface-deployed DAS data.

Purpose of the Study:

• To investigate improved ground-fiber coupling for DAS acquisition in shallow horizontal deployments.
• To re-evaluate processed DAS waveforms as filtered particle velocity.
• To enhance the quality and repeatability of seismic data from DAS.

Main Methods:

• Installing and freezing fiber optic cables in shallow (0.1 m depth) backfilled trenches.
• Acquiring seismic data using deformation-rate DAS.
• Applying 1D and 2D velocity-dip filtering to processed DAS waveforms.

Main Results:

• Improved coupling was achieved by freezing the fiber in backfilled trenches.
• DAS data reinterpreted as filtered particle velocity showed clear surface and refracted arrivals after 2D filtering.
• Data from frozen trench deployment exhibited higher repeatability and signal-to-noise ratios compared to surface-deployed fiber.

Conclusions:

• Deploying DAS fiber in backfilled, frozen trenches enhances seismic data quality and repeatability.
• This method mitigates environmental impacts on time-lapse DAS interpretations.
• The findings support reinterpreting DAS data as filtered particle velocity for improved geophysical analysis.