Seismogeodetic Super Array or Dirt-cheap Large-N? Evaluating fiber-optic DAS Instrument Response

Nate Lindsey

Stanford University

Date & Time
Online-only seminar via Microsoft Teams

Distributed Acoustic Sensing (DAS) is an emerging photonic method that transforms standard telecommunication optical fibers into meter-scale, watershed-aperture geophysical arrays. Such an idea has numerous possibilities in geoscience and civil engineering, for example in urban seismology, marine geophysics, and the cryosphere where observation is limited by access. The fomenting potential of DAS is belied by the method’s sparse calibration to-date. Developing an understanding of DAS instrument response is necessary for seismic moment tensor inversion, full-wavefield inversion, attenuation studies, and geodetic measurements of absolute strain. In this talk, evidence from recent laboratory and field experiments will be used to characterize DAS in terms of its frequency sensitivity, amplitude response, phase response, self-noise, and dynamic range. Behavior in the laboratory does not necessarily apply in the field due to fiber coupling and cable construction. To address this, two in situ field techniques will be proposed that use available seismological signals for calibration. Results will be shown from three field campaigns: FORGE geothermal microseismicity, regional and teleseismic earthquake observations in rural California, and microseisms recorded on the seafloor of Monterey Bay. I will conclude by summarizing the status of industry calibration standards, and discuss how greater awareness of DAS instrument response including inter-array comparisons could benefit the community.

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