Latitude: N 35°53'42"
Longitude: W 120°26'02"

Length: 3000.0m
Number of Bench marks: 28

Number of Surveys to 2000: 10
Date of Initial Survey: 7 April 1984 (UCSB)
Date of Latest Survey: 12 September 1996 (UCSB)

Trespass Permission: None needed.

Drive north on Highway 101 from Santa Barbara to Paso Robles, thence east on Highway 46 for 30 miles to Cholame. At a point 0.5 mile east of Cholame turn northwest onto Cholame Valley Road. Drive 14.4 miles to a green steel bridge and cross the bridge. Turn left onto Ranchita Road and drive 0.7 the intersection with an east-west road. BM 1526 is at the northwest corner of the intersection, near a fence junction.

This line was established across the San Andreas fault through the townsite of Parkfield by the U.S. Geological Survey in 1980.

Three UCSB levelings in the period 1984 to 1996 are compared in the graph below. Bench marks northeast of the San Andreas fault have negligible height changes relative to one another. The bench marks between the 0 and 1500 m distance marks subsided in apparent response to withdrawal of groundwater for irrigation in adjacent fields, or inresponse to the drought of 1983-1991.  The slight, but continued subsidence of bench marks southwest of the fault in 1993, relative to a bench mark on the northeast side, may be an indication that the subsidence has a tectonic component. 

Sylvester, A. G., 1995. Nearfield vertical displacement in the creeping segment of the San Andreas fault, central California, 1975 to 1994. Tectonophysics 247, 25-47.

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