Accession Number : AD0484050

Title :   DC SHIFT SEISMOMETER.

Descriptive Note : Final rept. 1 Aug 65-15 Jun 66.

Corporate Author : GM DEFENSE RESEARCH LABS SANTA BARBARA CA PHYSICAL SCIENCES DEPT

Report Date : JUN 1966

Pagination or Media Count : 79

Abstract : An automatic recording, continuously operating Pendulous Electric Vacuum Gyro (PEVG) Seismometer, the first of its kind, is described. The instrument is designed to be especially sensitive to small unrestored horizontal shifts (referred to as dc shifts) of the earth's crust during earthquake activity. The scientific background which motivated the project is discussed, the instrument is described, a digital computer program for reducing the data is described, and some conclusions from initial shakedown operation over a period of about one month are presented. Complete system operation was achieved in April 1966. Since then detailed studies of the random noise in the recorded readout data have been made because such noise has a direct bearing on the minimum detectable dc seismic shift. Indications are that the minimum detectable shift is less than 10 mm but more than 0.5 mm for the instrument in its present form supplemented by a near-optimum digital computer program for data reduction. Electrical noise picked up at the input terminals of the readout amplifiers (not internal gyro or amplifier noise) appears to be the major limiting factor.

Descriptors :   (*SEISMOMETERS, AUTOMATIC), FAULTS(GEOLOGY), LITHOSPHERE, EARTHQUAKES, SEISMIC WAVES, NUCLEAR EXPLOSIONS, SHOCK WAVES, SENSITIVITY, PERFORMANCE(ENGINEERING), NOISE, DIGITAL COMPUTERS, GYROSCOPES, BLAST, EQUATIONS OF MOTION, VACUUM APPARATUS.

Subject Categories : Seismology

Distribution Statement : APPROVED FOR PUBLIC RELEASE