Abstract
Distributed acoustic sensing (DAS) is a valuable tool for monitoring seismic signals as it provides high spatial and temporal resolution strain sensing along the length of a fiber-optic cable. DAS records the seismic wavefields essentially synchronously at each sensing location (i.e., sensing channel with gauge lengths) because the interrogator senses the distributed strain at the speed of light in the fiber. Unlike traditional seismic sensors, DAS has an intrinsic directional sensitivity to the axial strain change along the fiber, leading to difficulties when using standard seismic analysis and interpretations that rely on 3D particle velocity sensing. In addition, cable deployments on the surface can be dominated by high-amplitude wind or urban noise, impeding the detection of low-amplitude distant seismic sources. Here we investigate the capabilities of a unique 3D array with spiral-like portions in the Sanford Underground Research Facility (SURF), the former Homestake Mine, between 1250 m (4100 ft) and 1488 m (4850 ft) in depth for detecting local, regional, and teleseismic sources of ground vibrations. Our pilot array finds that DAS records high frequency (above 5 Hz) vibration sources well, such as mine activities and local and regional blasting events. Furthermore, our deployment method (fiber resting on the surface with rocks placed every meter or so) may contribute to low-frequency noise that contaminates the interpretation of teleseismic waves, particularly lower frequency S-wave arrivals. Nevertheless, this 3D DAS array provides significant data for future analysis as well as the basis for improving and expanding the array in SURF.
| Original language | English |
|---|---|
| Pages (from-to) | WC209-WC220 |
| Journal | Geophysics |
| Volume | 88 |
| Issue number | 6 |
| DOIs | |
| State | Published - Nov 1 2023 |
Funding
The research supporting this work took place in whole or in part at the Sanford Underground Research Facility (SURF) in Lead, South Dakota. We greatly appreciated the support from SURF by J. Heise, M. Horn, B. Pietzcyk, and J. Tollefson We received excellent support from Ray Sutyla of Optasense, who set up and operated their DAS interrogator remotely from Houston. B. Roggenthen of the South Dakota School of Mines & Technology guided us to documents needed for our data analysis and interpretation. Funding for this work is supported by the University of Wisconsin-Madison’s Research Forward project “Internet Photonic Sensing: Using Opportunistic Internet Measurements for Vibration and Earth Motion.” This material is based on research sponsored also by Air Force Research Laboratory (AFRL) under agreement number FA9453-21-2-0018 as a subaward from Stanford University “Towards Enhanced Seismic Monitoring with Distributed Acoustic Sensing.” The U.S. Government is authorized to reproduce and distribute reprints for Governmental purposes notwithstanding any copyright notation thereon. The views and conclusions contained herein are those of the authors and should not be interpreted as necessarily representing the official policies or endorsements, either expressed or implied, of Air Force Research Laboratory (AFRL) or the U.S. Government. The research supporting this work took place in whole or in part at the Sanford Underground Research Facility (SURF) in Lead, South Dakota. We greatly appreciated the support from SURF by J. Heise, M. Horn, B. Pietzcyk, and J. Tollefson We received excellent support from Ray Sutyla of Optasense, who set up and operated their DAS interrogator remotely from Houston. B. Roggenthen of the South Dakota School of Mines & Technology guided us to documents needed for our data analysis and interpretation. Funding for this work is supported by the University of Wisconsin-Madison’s Research Forward project “Internet Photonic Sensing: Using Opportunistic Internet Measurements for Vibration and Earth Motion.” This material is based on research sponsored also by Air Force Research Laboratory (AFRL) under agreement number FA9453-21-2-0018 as a subaward from Stanford University “Towards Enhanced Seismic Monitoring with Distributed Acoustic Sensing.” The U.S. Government is authorized to reproduce and distribute reprints for Governmental purposes notwithstanding any copyright notation thereon. The views and conclusions contained herein are those of the authors and should not be interpreted as necessarily representing the official policies or endorsements, either expressed or implied, of Air Force Research Laboratory (AFRL) or the U.S. Government.