UNA LAKE Level Line

Latitude: N 34°33'00"
Longitude: W 118°6'15"

Length: 1250m
Number of Bench marks: 15

Number of Surveys to 2000: 7
Date of Initial Survey: 22 August 1979
Date of Latest Survey: 15 September 1994

Trespass Permission: None needed.

Directions: From the center of Palmdale, proceed south 2 miles along Old Sierra Highway, parallel to the railroad track to Avenue S. The UCSB part of the array commences at Avenue S and proceeds southward along the railroad track to a point near the Harold siding.

This is one of several fault crossing lines established across the San Andreas fault by the U.S. Coast and Geodetic Survey (NGS) in 1935. The UCSB array covers only part of the entire NGS array which is along the railroad track, 2 miles south of Palmdale.

Six levelings of the line from 1979 to 1989 are compared in an accompanying figure and show that height changes among the bench marks are minimal in that time period, although a case may be made for a southwest tilt of the line of about 5 microradians.

Bench marks A428, B428, C428, D428, G811, G488, F488 were destroyed by the installation of GTE/Sprint fiber optic cable. The line now begins at bench mark D488, approximately 350 meters south of Avenue S along Sierra Highway. Benc h marks P428, Z487, Y487, and X487 could not be found during the September 1994 survey and are presumably buried by recent earthmoving.

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