ReMi-DAS

Refraction Microtremor Processing for Distributed Acoustic Sensing Data

ReMi-DAS is an open-source toolkit for applying Refraction Microtremor (ReMi) analysis to Distributed Acoustic Sensing (DAS) data.
It extends conventional ReMi workflows to accommodate strain/strain-rate measurements from DAS arrays, enabling efficient and scalable shear-wave velocity (Vs) profiling—particularly in urban or infrastructure-constrained environments.

Author: Shihao Yuan (syuan@mines.edu)

DISCLAIMER: This is a development build. The code may contain errors or unstable functionality. Contributions and feedback are welcome.

This package is developed using core functionality from the DASCore project — a flexible Python library for reading, processing, and visualizing DAS data.

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Features

• A Jupyter notebook demonstrating the complete ReMi workflow
• Modular Python scripts for:
  • Preprocessing DAS data (e.g., tapering, filtering)
  • Slowness-frequency transformation using Tau-P methods
  • Dispersion curve picking and visualization
• Tools for slowness-frequency image plotting and Rayleigh-wave dispersion analysis

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Synthetic study

The notebook notebooks/ReMi-DAS-synthetic.ipynb provides a synthetic study that:

• Generates ambient traffic-noise fields and simulates DAS strain-rate along a fiber using the src/noise_synthetics module.
• Exports synthetic data to a DASCore Patch and runs the same ReMi workflow end-to-end (tapering, f–p transform, dispersion picking).

This is useful for checking parameters and understanding expected dispersion features before applying the workflow to field datasets.

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How synthetic traffic noise is generated

• Event process: vehicle pass-bys are modeled as a Poisson process (rate per minute), with random amplitudes and durations (exponential about a mean).
• Source geometry: each event samples an azimuth (Gaussian or weighted cones) and a source distance (fixed list or uniform/area-weighted ring). Amplitude optionally decays with distance.
• Source time function: either colored noise shaped to a traffic band (≈1–49 Hz) with optional spectral tilt, or a Ricker pulse; windowed with a raised-cosine taper.
• Propagation: events are projected as plane waves using a dispersion relation k(f)=ω/c(f) from a user-specified medium; phase delays are applied across the linear array.
• Strain-rate: derived in the frequency domain by multiplying by −i·ω·k·cos(θ); both displacement and strain-rate can be returned.

References

• McMechan, G.A. and Yedlin, M.J., 1981. Analysis of dispersive waves by wave field transformation. Geophysics, 46(6), pp.869-874.
• Louie, J.N., 2001. Faster, better: shear-wave velocity to 100 meters depth from refraction microtremor arrays. BSSA, 91(2), pp.347-364.
• Chambers, D., Jin, G., Tourei, A., Issah, A.H.S., Lellouch, A., Martin, E.R., Zhu, D., Girard, A.J., Yuan, S., Cullison, T. and Snyder, T., 2024. Dascore: A python library for distributed fiber optic sensing. Seismica, 3(2), pp.10-26443.