Latitude: N 34°29'30"
Longitude: W 117°58'04"
Number of Bench marks: 20
Number of Surveys to 2000: 5
Date of Initial Survey: 9 August 1989
Date of Latest Survey: 16 July 1996
Kinematic GPS Survey: July 1997
Trespass Permission: None needed.
From Palmdale proceed east and southeast on 138 to the town of Littlerock. Continue east beyond the town to 96 th St. East and turn right. A Pacific Bell substation is located on the corner of Hwy 138 and 96 th St. East. Proceed to Fort Tejon Road and turn left, but turn right almost immediately on the first dirt road. Continue south about 200 m until the road comes to a "T" and turn right at the "T". Drive about 0.3 mile and take a left onto a dirt road heading south. The dirt road intersects the middle of the leveling line about 30 m before the base of a prominent southeast-trending ridge west of the road.
This array was established across the San Andreas fault where Dr. David Schwartz (US Geological Survey) dug a series of trenches across the fault to determine its paleoseismicity. A trebly-braced, nearfield quadrilateral also spans the fault at this locat ion to determine horizontal strain.
Observed height changes are within the allowable error for the four surveys between 1989 and 1996, as is shown in the figure below. Bench mark LR11 was unstable in 1991 relative to the others.
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