Latitude: 33š35'00"
Longitude: 116š39'40"

Number of Bench marks: 4

Number of Surveys to 1993: 2
Date of Initial Survey: 20 July 1990
Date of Latest Survey: 24 June 1992

Trespass Permission: Most of the array is on private property with limited access to authorized persons. It is a good idea to notify in advance Mr. Larry Muzzall (714) 763-4816) who owns the adjacent property to the southeast, as well as the gate to access the array.

Directions: From Riverside take Interstate 15E 40 miles south to State 79 South, then proceed east 18 miles to State 371, and then east (left turn) on Hwy 317 for 15 miles to Anza. At the intersection of 371 and Hill St. in Anza, turn left (north) on Hill S treet Drive and proceed 1.1 miles to Mitchell Street. Turn right and drive 0.5 mile to Bohlen Street (after the Hamilton School). Turn left on Bohlen Street and drive 0.8 mile to the end of the road, up to a gate leading to USFS road 6520. Drive through the left gate along a dirt road to Pine Oaks and Rancho de la Detras. The array is about 0.5 miles from the gate, and straddles the dirt road which follows the San Jacinto fault trace.

Comments: Early UCSB surveys of this quadrilateral measured slope l engths with an HP3808A distance meter. Redundant shots of all lines were first performed in 1990 using a Wild TC2000 total station distance meter. Bench marks are Class B rod marks driven to refusal and capped with a stainless steel nipple. No significa nt horizontal displacement was detected at this array following a increased in the seismicity in December 1989 (Sylvester, et al., 1990), however, both diagonals apparently shortened in 1992 by an amount equal to about ten times the uncertainty in the meas urements.

Sylvester, A. G., J. Helm, C. Hitchcock, and N. Howe, 1990. Minor vertical, but no horizontal nearfield displacement across the San Jacinto fault at Anza and San Bernardino, California, from 1988 to 1990. Seismological Research Letters 61 (1), p. 22.

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