Calibrated DAS Moment Magnitudes: Moving from Strain to Ground Motion Using Downhole Microseismic Monitoring Data
conference paper
Distributed acoustic sensing (DAS) provides axial strain measurements along optical fibers whereas ground motion quantities can be required for interpretation or inversion processes. Using co-located DAS and reference accelerometer records from the downhole monitoring setup of the FORGE (Frontier Observatory for Research on Geothermal Energy) site, we apply a DAS transfer function workflow to obtain calibrated velocity records of microseismic events from initial DAS (strain rate) measurements. The calibration workflow is based on the conversion of physical units using frequency-wavenumber domain transformations and on the correction of the remaining misfit to the reference. This misfit, which corresponds to a factor of approximately two for the P-wave arrivals, is quantified in terms of a frequency response in the range 50–200 Hz. We analyze such DAS system responses as a function of the co-located depth positions and we show that, after corrections, we can determine the moment magnitude (Mw) reliably from DAS for microseismic events with Mw > −0.9.
TNO Identifier
994689
ISBN
9789462824966
Publisher
European Association of Geoscientists & Engineers
Source title
EAGE GeoTech 2024 Fourth EAGE Workshop on Distributed Fibre Optic Sensing, April 2024
Pages
1-5
Files
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