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Experimental and Theoretical Studies of Long-Period Tilt of Earth's Crust: Part I. Experimental.
Final rept. (Part 1), 9 Dec 69-9 Jul 71,
LITTLE (ARTHUR D) INC CAMBRIDGE MASS
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A three-element borehole tiltmeter system was developed and installed at Bedford, Massachusetts for the purpose of measurement and analysis of crustal tilts. Each borehole unit contains two single-axis tiltmeters with diamagnetically suspended masses and leveling motors adapted for stepwise calibration in situ. Individual wellhead electronic units contain regulated power supplies, low-pass filter-amplifiers and controls for remote leveling. Output signals are transmitted by cables to a central terminal where they are monitored with strip-chart recorders and recorded by a multi-channel digital tape recorder. The three boreholes, 50 to 56 ft. deep and approximately 600 feet apart, are in a compact, foliated granitic gneiss overlain by 3 to 10 ft. of overburden. They have steel casing extending approximately 20 feet below surface. Water level stands approximately 8 - 10 ft. below the surface. The system has been in operation for over a year now and considerable amount of data on tidal tilts and their perturbations was obtained. Author
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