Earthquake strain sensing using optical fiber interferometers

Surui Xie, Mark A. Zumberge, & Rob Mellors

Submitted August 16, 2021, SCEC Contribution #11582, 2021 SCEC Annual Meeting Poster #235

Two horizontal (trench lengths: 200 and 225 m) and one vertical (borehole depth: 250 m) stretched optical fiber strainmeters (OFS) were developed to measure Earth strain by monitoring laser light interferometrically. These OFSs are capable of measuring both static and dynamic strain with high precision. They are, in a sense, equivalent to one single extended gauge length of a DAS and hence provide useful constraints on how DAS measurements compare with co-located seismometers. We compared the performance of these OFSs with a collocated array of broadband and very broadband seismometers (installed by F. Vernon) by projecting seismometer-derived strain onto the OFS longitudinal directions; several representative earthquakes are presented here. The OFSs measured earthquake arrival time and amplitude of dynamic response well. From a signal-to-noise ratio (SNR) perspective, the quality of data collected by the OFSs are equivalent to seismometers over a broad frequency range. Inferring strain by differentiating data collected by two nearby seismometers does not appear to yield results as clear as those from comparing to a single seismometer.

Key Words
optical fiber, strainmeter, seismometer

Xie, S., Zumberge, M. A., & Mellors, R. (2021, 08). Earthquake strain sensing using optical fiber interferometers. Poster Presentation at 2021 SCEC Annual Meeting.

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