Fiber Optic Sensing of Local and Regional Earthquakes

Date: 4/24/2019

Time: 08:45 AM

Room: Grand Crescent

Fiber optic distributed acoustic sensors (DAS) are becoming a widely used tool for seismic sensing for both active and passive measurements. DAS sensors possess several advantages such as low-cost high spatial resolution and wide bandwidth response, but also includes disadvantages such as one component of measurement and a higher noise floor. Here we explore the components of the typical system response (interrogator, fiber/cable, and coupling) and the expected response along with an assessment of the potential for future improvements. Validation of the estimated response is ongoing using a custom interrogator and a fiber testbed. We then apply this understanding to measurements of local and regional events including full waveform modelling and earthquake parameters inferred from coda measurements using data from fiber sensors. We focus on a magnitude 4.3 (21 March 2016 at 07:37) earthquake recorded at a distance of 150 km by a multi-orientation (zig-zag) surface fiber deployment at Brady geothermal area that was co-located with a geophone array, allowing comparison of measurements between geophones and fiber recordings. Synthetic seismograms generated using a known moment tensor matched both the three-component geophones and, when converted to linear strain, the fiber data. Coda wave technique, which allow estimation of source parameters such as magnitude, were also consistent between the fiber and the geophone array. Coda waves are scattered waves and therefore are not as sensitive to fiber orientation. Finally, we speculate on possible key science advances that might be enabled by this new technology.

Presenting Author: Robert J. Mellors

Authors