Session: Sensing Technologies and their Latest Developments [Poster]
Type: Poster
Date: 10/7/2024
Time: 05:00 PM
Room: Stanley Park Ballroom
Calibrating Strain Measurements: A Comparative Study of DAS, Strainmeter, and Seismic Data
Distributed Acoustic Sensing (DAS) measures strain along an optical fiber at specific intervals. Although converting DAS strain into ground units seems straightforward, practical implementation can result in coupling and instrument response errors. To address this, we compared DAS strain measurements with total strain from an optical fiber strainmeter (OFS) within the same cable. We also simulated strain using single-point velocity measurements from a nearby broadband STS2 seismometer.
Our study includes both field and lab experiments. In the field, DAS and OFS were deployed together on Whidbey Island, Washington, on land and beneath a shallow waterway. We used a teleseismic event recorded by DAS and converted it to total strain by stacking recordings from each channel. The integrated DAS strain data were then compared with OFS measurements, showing highly similar waveforms, nearly identical amplitudes, and a correlation coefficient above 0.95. Strain simulations from seismic velocity also showed consistency with offshore recordings, though with an amplitude factor of ~2.5, suggesting imperfect coupling between the fiber and the ground.
In the lab, we introduced a new method for evaluating DAS amplitude response using DAS and OFS. This method employs a piezoelectric sensor to generate ground truth strain, avoiding biases from natural earthquakes. Lab findings indicated a -3.2 dB decrease in DAS recorded amplitude at low frequencies (0.01 Hz), emphasizing the need for amplitude calibration in such studies.
Our investigation of underwater signals revealed a strong correlation with tide speed, with signals concentrated around slope turning points on the eastern side. This localization was achieved by calculating the coherence between DAS and OFS recordings, providing insight into the unknown source of these underwater signals.
Presenting Author: Chih-Chieh
Additional Authors
Chih-Chieh Chien cchien@ucsd.edu University of California, San Diego, La Jolla, California, United States Presenting Author
|
Bradley Lipovsky bpl7@uw.edu University of Washington, Seattle, Washington, United States |
Dale Winebrenner dpw@uw.edu University of Washington, Seattle, Washington, United States |
Leo Hollberg leoh@stanford.edu Stanford University, Stanford, California, United States |
Mark Zumberge mzumberge@ucsd.edu University of California, San Diego, La Jolla, California, United States Corresponding Author
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Peter Gerstoft pgerstoft@ucsd.edu University of California, San Diego, La Jolla, California, United States |
Robert Mellors rmellors@ucsd.edu University of California, San Diego, La Jolla, California, United States |
William Hatfield whatfield@ucsd.edu University of California, San Diego, La Jolla, California, United States |
Calibrating Strain Measurements: A Comparative Study of DAS, Strainmeter, and Seismic Data
Category
Sensing Technologies and their Latest Developments
Description