BARREL EDM Array
Number of Bench marks: 5
Number of Surveys to 1993: 2
Date of Initial Survey: 12 September 1990
Date of Latest Survey: 20 June 1991
Trespass Permission: None required.
Directions: The array is 6 km southeast of Palmdale and 6 km west of Littlerock, and about 1 km SE on Barrel Springs Road from its intersection with Pearblossum Hwy.
Comments: This array was established by the National Geodetic Survey across the San Andreas fault and the California Aqueduct in 1964. Bench marks are standard NGS bronze tablets in concrete posts. Previous NGS surveys were in 1964, 1965, 1966, 1967, 1970, and 1 971. It was surveyed by the California Division of Mines & Geology in May 1978. The 1971 NGS and 1978 CDMG measurements were made with the same model EDM instrumentation (Tellurometer MA-100). The 1978 CDMG measurements revealed no significant horizontal fault movement during the 7-year period 1971-1978, and first-order releve ling by the Los Angeles County Engineer in November 1977 similarly indicated no differential vertical movement within this survey network during the period 1971-1978 (Bennett, 1979). The two UCSB surveys were performed with a Wild TC2000 total station dis tance meter. Relative to the 1971 NGS survey, all the line lengths increased from 70 to 130 mm. The increase is probably due to different reflector constants between the two different instruments. Line lengths from September 1990 to June 1991, using the UCSB TC2000, are comparable with allowable uncertainty.
Bennett, J. H., 1979. Fault creep measurement. California Geology 32, 98-105.
U.S. Department of Commerce, Coast & Geodetic Survey, July 1971
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