Published August 5, 2024 | Published
Journal Article Open

Fiber-optic seismic sensing of vadose zone soil moisture dynamics

  • 1. ROR icon California Institute of Technology
  • 2. ROR icon Woods Hole Oceanographic Institution
  • 3. ROR icon Jet Propulsion Lab

Abstract

Vadose zone soil moisture is often considered a pivotal intermediary water reservoir between surface and groundwater in semi-arid regions. Understanding its dynamics in response to changes in meteorologic forcing patterns is essential to enhance the climate resiliency of our ecological and agricultural system. However, the inability to observe high-resolution vadose zone soil moisture dynamics over large spatiotemporal scales hinders quantitative characterization. Here, utilizing pre-existing fiber-optic cables as seismic sensors, we demonstrate a fiber-optic seismic sensing principle to robustly capture vadose zone soil moisture dynamics. Our observations in Ridgecrest, California reveal sub-seasonal precipitation replenishments and a prolonged drought in the vadose zone, consistent with a zero-dimensional hydrological model. Our results suggest a significant water loss of 0.25 m/year through evapotranspiration at our field side, validated by nearby eddy-covariance based measurements. Yet, detailed discrepancies between our observations and modeling highlight the necessity for complementary in-situ validations. Given the escalated regional drought risk under climate change, our findings underscore the promise of fiber-optic seismic sensing to facilitate water resource management in semi-arid regions.

Copyright and License

© The Author(s) 2024.

This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.

Acknowledgement

We thank Santiago G. Solazzi for discussions on rock physics modeling from soil moisture to dv/v. This study is supported by the National Science Foundation CAREER #1848166 and the Resnick Institute of Sustainability. We are grateful to the field and technical support from Martin Karrrenbach, Lisa LaFlame, Vlad Bogdanov of Optasense Inc., Thomas Coleman of Silixa Inc., and Andrew Klesh of Jet Propulsion Laboratory. We thank the California Broadband Cooperative and JPL for providing access to the Digital 395 telecommunication fibers. Z.S. also thanks the support from the Weston Howland Jr. Postdoctoral Scholar Program at Woods Hole Oceanographic Institution.

Contributions

These authors contributed equally: Zhichao Shen, Yan Yang.

Z.S. and Z.Z. conceptualized this study. Z.S., Y.Y., X.F., and Z.Z. developed the methodology. Z.S. and Y.Y. processed the data, and conducted the investigations with X.F., K.H.A., E.B., and Z.Z. together. Z.S. and Y.Y. contributed to the visualization. E.B. and Y.Y. contributed to the data management. Z.S. and Y.Y. drafted the original manuscript, and all the authors reviewed, edited, and refined the manuscript.

Data Availability

The cross-correlation product and multi-frequency dv/v generated in this study have been deposited in Zenodo under the accession code https://doi.org/10.5281/zenodo.12617908. The precipitation data used in this study are available in the California Nevada River Forecast Center under accession code https://www.cnrfc.noaa.gov/arc_search.php. The groundwater well data used in this study are available in the Indian Wells Valley Groundwater Authority under accession code https://iwvgsp.com/. The surface temperature and surface soil moisture data used in this study are available from the National Snow and Ice Data Center under accession code https://nsidc.org/data/smap/dataSource data are provided in this paper.

Code Availability

The GPU-based ambient noise cross-correlation code can be downloaded from https://github.com/zhichaoshen40/DAS_CC_GPU.git.

Supplemental Material

Supplementary Information

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Additional details

Created:
February 24, 2025
Modified:
February 24, 2025