Latitude: N 35°53'38"
Longitude: W 120°26'32"
Length: 90.0m
Number of Bench marks: 12
Number of Surveys to 2000: 4
Date of Initial Survey: 27 June 1989
Date of Latest Survey: 22 June 1993
Trespass Permission: Ranch is occupied. Permission to trespass is
required.
Directions:
From the bridge at Parkfield, drive northwest on Vineyard Canyon Road 0.6
mile to the Owens Ranch gate (now called Bennett Ranch). The line begins
about 100 m north of the gate. The first bench mark (XPK5) may be buried
and difficult to find.
Comments:
The bench marks in this array belong to an alignment that was established
by Dr. Jeremy Isenberg to determine the performance of buried pipelines in
earthquakes. Only the end bench marks are Class B standard. The remainder
are plastic stakes on top of the pipeline.
Results:
The three levelings suggest that the northeast side of the fault subsided
about 15 mm relative to the southwest side since 1989, but not at the fault
trace.
References:
Isenberg, J., E. Richardson, H. Kameda, and M. Sugito, 1990. Pipeline response
at Parkfield, CA. to Loma Prieta earthquake. Proceedings of Fourth U.S. National
Conference on Earthquake Engineering, vol. 1, 925-933.
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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