Latitude: N 34°25'10"
Longitude: W 117°54'00"
Length: 1656m
Number of Bench marks: 70
Number of Surveys to 2000: 16
Date of Initial Survey: 22 June 1978
Date of Latest Survey: 10 August 1989
Trespass Permission: The line is on private ranch property:
Ranch Manager, Carol Robinson
12880 Juniper Hills Road
Pearblossom, CA 93553
(805) 944-5518
Directions:
From Palmdale, proceed east and sout heast 27 miles to Pearblossom, thence
south about 5 miles on Longview Road to its southernmost point which is at
a fence and gate into the Mountain Glen Ranch. The first bench mark is on
the north side of the fence about 2 m west of the gate. The line pr oceeds
southward along the west side of the dirt road that leads up the creek on
the ranch property.
Comments:
This line crosses the Punchbowl fault along the northwest bank of Pallett
Creek, six miles south of Pearblossom. It was established to determin ed
if a swarm of earthquakes in the Juniper Hills area during the late 1970s
was having an effect on the Punchbowl fault.
A plane recently crashed into the Pallett Creek level line area. The road
that the level line follows was widened to allow heavy equipment access to
the crash site. Many bench marks were bulldozed out, crushed, or pushed farther
into the ground. This li ne needs to be restored before another survey can
be done.
Results:
The first and latest levelings in the period 1978 to 1989 are compared in
an accompanying figure with marginal evidence for about 1.5 mm of vertical
displacement across the fault. The sense of displacement is mountain side
down, and the location of the fault at the base of the high San Gabriel Mountains
would pond g roundwater south of the fault. Thus, the sense of displacement
is opposite to what one would expect from the recent geologic uplift of the
mountains or from the lowering of the water table north of the fault during
the 1986-1991 drought.
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