Development of a New Broadband Optical Seismometer

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EAR-0352877Zumberge World-wide seismic networks are increasingly complex and require seismometers that can detect Earth vibrations spanning a wide range of amplitude and frequency. The mainstay observatory-class seismometer used by global networks for the past two decades is no longer manufactured and there is no other commercially available product of sufficient quality on the market today. For such quality instruments, the development risk is high, the development time long, and the market small and apparently not sufficient to provide commercial viability. To meet the instrumentation requirements of global seismology, we will design, build and test a new observatory-class seismometer that will use optical fiber interferometry to record the motion of a small mass suspended on a spring. The use of optical fiber interferometry rather than traditional electronic displacement transducers affords significant advantages. At the conclusion of this proposed program, we expect to have developed, built and tested a new observatory-class seismometer suitable for either vault or borehole installation. The proposed research is important to advancing our knowledge of Earth because it will ultimately result in clearer seismic images of the interior. It will also provide for better observations from within boreholes, where the inherent seismic signal-to-noise ratio is better. In the process, we will have further developed a displacement sensor of sufficient sensitivity, dynamic range and bandwidth not only to satisfy the requirements of observatory-class seismology but with applications to other fields as well.