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Sensors Developed in the US for Low Frequency Seismology. W. E. Farrell Science Applications International Corp. Topics. Summary Motivation Nuclear test detection Physics and geophysics Geotech KS series Other Geotech sensors Academic projects. Summary.
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Sensors Developed in the US for Low Frequency Seismology W. E. Farrell Science Applications International Corp
Topics • Summary • Motivation • Nuclear test detection • Physics and geophysics • Geotech KS series • Other Geotech sensors • Academic projects
Summary • The principal driver for 1/2 century of development of LP sensors has been nuclear test monitoring • The heyday lasted a long time, 1958-2000 • Currently here seems to be little interest within DoD or DoE for R&D in LP sensors • Much innovation came from University programs • Academics partly rode on the shirt tails of the test detection funding, but were focused on fundamental problems • NSF and private foundation money was key to these programs • AFOSR was a supporter in the early years • Sensor R&D in universities tapered off through the 70s • Perception that available technology good enough?
Motivation - Nuclear Test Detection • The problem of nuclear test detection has generated the most money for R&D in long period sensors • Berkner Report 1959 • Mb:Ms discriminant requires good SNR in the .1-.03Hz range • Lower frequency data required for estimating shallow earth structure, but ultra low frequencies were not a concern • Borehole packaging deemed critical • DARPA & Vela Uniform • See Farrell, 1985, Sensors, Systems & Arrays • AFTAC • Sponsored sensor R&D related to its monitoring mission • DOE
Motivation - Physics and Geophysics • Fundamental research in physics & geophysics has been an equally important driver of progress • Dicke • Theories of gravity • Lock-in amplifiers, capacitor pickoff & electrostatic feedback • IDA • Systematic observation of free oscillations for splitting and Q(r) • Inherited and applied Dicke approach • Superconducting gravity meter • “Zero” drift would lead to data in the tectonic frequency band • A few in service as seismometers • Strain meters